At which OSI layer do cables, connectors, radio signals, and raw bits belong?

Layer 1 — Physical. It moves bits across the medium and defines electrical, optical, radio, connector, and signaling details.

A LAN needs forwarding by MAC address, while traffic between IP networks needs forwarding by destination IP. Which appliances fit each job?

A switch handles the LAN forwarding; a router connects the IP networks. A switch learns Layer 2 MAC addresses, while a router selects Layer 3 paths.

What does a virtual private cloud provide?

An isolated logical network in a cloud. You choose address ranges, subnets, routes, gateways, and traffic controls while logical boundaries separate tenants on shared provider infrastructure.

Which well-known ports does FTP use, and why are there two?

TCP 21 for control and TCP 20 for the traditional active-mode data channel. FTP is unencrypted; secure file transfer normally uses a different protocol such as SFTP.

When is single-mode fiber preferred over multimode fiber?

For longer distances and higher reach. Single-mode uses a smaller core and typically a laser source; multimode is common for shorter links and usually costs less at the endpoints.

What is the main operational tradeoff of a star topology?

A single access link failure usually affects one node, but failure of the central device can affect the whole star. Centralization also makes changes and fault isolation simpler.

Which three IPv4 ranges are reserved for private networks by RFC 1918?

10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Public routers should not treat these as globally routable destination space.

How do SDN, SD-WAN, and NFV differ?

SDN separates programmable control from data forwarding across a network. SD-WAN applies that approach to WAN overlays, using central policy and path conditions to steer traffic across transports. NFV runs network functions as software instead of tying each one to a dedicated appliance.

At which OSI layer are Ethernet frames, MAC addresses, and switching decisions handled?

Layer 2 — Data Link. It packages bits into frames and delivers them across a local link using hardware addresses and link-level control.

How does an IPS differ from an IDS in the traffic path?

An IPS sits inline and can block traffic; an IDS detects and alerts from observed traffic. Inline enforcement adds prevention but also makes availability and tuning more important.

In a typical VPC, how do a security group and a network ACL differ?

A security group filters traffic at a resource interface and is usually stateful; a network ACL filters at the subnet boundary and is stateless. Exact behavior is provider-specific, so verify the platform.

Which ports distinguish SSH/SFTP from Telnet?

SSH and SFTP use TCP 22; Telnet uses TCP 23. SSH encrypts the session, while Telnet sends the session without that protection.

What is a direct-attach copper cable in a data-center link?

A short twinax assembly with transceiver ends fixed to the cable. It is a low-power, low-latency option for nearby switches and servers, but its reach is limited.

Why does a spine-and-leaf fabric suit east-west data-center traffic?

Every leaf connects to every spine, giving a predictable small hop count between endpoints. Adding spines or leaves scales capacity without building a long hierarchical path.

A Windows host self-assigns 169.254.24.8/16. What does that suggest?

APIPA/link-local addressing. The host did not obtain its intended IPv4 configuration, commonly because DHCP was unavailable; the address works only on the local link.

How do VXLAN and data center interconnect relate?

VXLAN carries Layer 2 overlays across an IP underlay; data center interconnect (DCI) links separate data-center sites. A DCI design can extend selected VXLAN segments or exchange routed reachability between sites, but DCI is the inter-site function, not a synonym for VXLAN.

At which OSI layer do IP addressing and routing belong?

Layer 3 — Network. It provides logical addressing and selects paths across interconnected networks.

What is the difference between a forward proxy and a reverse proxy?

A forward proxy acts for clients reaching servers; a reverse proxy acts in front of servers receiving client requests. Both can mediate, filter, cache, or hide the systems behind them.

A private cloud subnet needs outbound internet access without accepting unsolicited inbound connections. Which gateway fits?

A NAT gateway. It translates outbound flows for private addresses and permits return traffic for those flows; an internet gateway alone does not make a private-addressed host reachable.

Which well-known ports map to SMTP and DNS?

SMTP uses TCP 25 for server-to-server mail transfer; DNS uses UDP or TCP 53. DNS commonly uses UDP for ordinary queries and TCP when required by size or operation.

Why is plenum-rated cable required in some air-handling spaces?

Its jacket is designed for stricter flame-spread and smoke requirements. Local fire and building codes decide where it is required; ordinary PVC-jacket cable may not be acceptable there.

What are the three layers in the classic three-tier campus design?

Access, distribution, and core. Access connects endpoints, distribution aggregates access and applies policy, and the core provides fast resilient transport between distribution blocks.

What does the IPv4 loopback range test?

The local host's IP stack. The range is 127.0.0.0/8, with 127.0.0.1 commonly used as localhost; packets never need to reach a physical network.

What trust assumption does zero trust architecture reject?

It rejects implicit trust based only on network location or ownership. Access is evaluated for the user, device, resource, and context, then limited to what policy allows.

At which OSI layer do TCP and UDP ports, segmentation, and end-to-end transport belong?

Layer 4 — Transport. It identifies application endpoints with ports and provides transport behavior such as reliable streams with TCP or datagrams with UDP.

How do NAS and SAN present storage differently?

NAS presents shared files over the network; a SAN presents block storage to hosts. NAS fits file sharing, while SAN-attached storage looks more like a locally attached disk to the server.

How do SaaS, PaaS, and IaaS divide customer responsibility?

SaaS supplies the finished application, PaaS supplies an application platform, and IaaS supplies virtualized compute/network/storage. Customer control and operational responsibility generally increase from SaaS to PaaS to IaaS.

Which ports map to DHCP, TFTP, and HTTP?

DHCP uses UDP 67/68, TFTP uses UDP 69, and HTTP uses TCP 80. DHCP separates server and client ports; TFTP is a simple unauthenticated transfer protocol.

What is the practical difference between SFP and QSFP form factors?

SFP is a small pluggable transceiver family for one link lane; QSFP groups four lanes in a compact module. The suffix and module specification, not the shape alone, determine supported speed and medium.

In data-center terminology, how do north-south and east-west traffic differ?

North-south traffic enters or leaves the data center; east-west traffic moves between internal systems. The distinction helps choose firewall, load-balancing, and fabric capacity placement.

A /27 IPv4 subnet has how many addresses and normally how many usable host addresses?

32 total and 30 normally usable. Five host bits remain, so 2^5 = 32; the network and broadcast addresses are not assigned to ordinary hosts.

How does SSE relate to SASE?

SSE is the cloud-delivered security-services portion; SASE combines those security services with wide-area networking. Implementations vary, but SASE joins connectivity and policy closer to users and resources.

At which OSI layer are sessions established, coordinated, and torn down?

Layer 5 — Session. The conceptual layer manages dialogs and checkpoints between applications, even though real protocol stacks often combine its work with other layers.

How do an autonomous access point and a controller-based access point differ?

An autonomous AP holds its own control configuration; a lightweight AP relies on a controller for centralized policy and coordination. Controller designs simplify consistent changes across many APs.

How do public, private, and hybrid cloud deployment models differ?

Public cloud uses provider-operated shared infrastructure, private cloud is dedicated to one organization, and hybrid connects private and public environments for a combined design.

Which ports map to NTP and SNMP?

NTP uses UDP 123. SNMP queries commonly use UDP 161, while notifications such as traps commonly use UDP 162.

Which common fiber connectors are push-pull, small-form-factor latch, bayonet, and multifiber?

SC is push-pull, LC is the smaller latched connector, ST uses a bayonet twist, and MPO carries multiple fibers in one connector. Always match polish, fiber type, and transceiver requirements too.

What makes a hybrid topology different from a mesh topology?

A hybrid combines two or more topology patterns; a mesh emphasizes multiple interconnections and alternate paths among nodes. A design can be both hybrid and partially meshed.

Which first-octet ranges identify the historical IPv4 classes A through E, and how do CIDR and VLSM differ from that model?

Class A is 1–126 with a default /8, Class B is 128–191 with /16, and Class C is 192–223 with /24; these were classful unicast ranges. Class D is 224–239 for multicast, while Class E is 240–255 and reserved. The 0/8 and 127/8 blocks are special. Modern CIDR uses explicit prefixes, and VLSM lets subnets use different prefix lengths instead of fixed class boundaries.

What operational problem does infrastructure as code solve?

It makes infrastructure definitions repeatable, reviewable, and versioned. Templates and automation reduce manual drift, while source control exposes changes, conflicts, and rollback history.

Which OSI layer handles data representation tasks such as format translation, compression, and encryption?

Layer 6 — Presentation. It describes how applications agree on representation, though modern protocol suites often place these functions inside application protocols or libraries.

How do cloud scalability and elasticity differ?

Scalability is the ability to handle growth by adding resources; elasticity adjusts resources up or down with demand. Elasticity emphasizes timely, often automatic, resizing.

Which ports map to LDAP, HTTPS, and SMB?

LDAP uses TCP/UDP 389, HTTPS uses TCP 443, and SMB commonly uses TCP 445. Encryption depends on the protocol and configuration, not merely on reaching a familiar port.

Which connector is typical for Ethernet twisted pair, and which two appear on common coax runs?

RJ45 is typical for Ethernet twisted pair; F-type and BNC are common coax connectors. RJ11 is smaller and is commonly associated with telephone cabling.

At which OSI layer do user-facing network services such as HTTP and DNS sit?

Layer 7 — Application. It is the top conceptual layer where network services are exposed to applications and users.

Why can a content delivery network reduce page latency?

It serves cacheable content from distributed edge locations closer to users. The shorter path and offloaded origin reduce delay and origin demand when caching rules fit the content.

Which ports map to Syslog, secure mail submission, and LDAPS in the N10-009 blueprint?

Syslog uses 514, secure SMTP submission uses 587, and LDAPS uses 636. Transport details can vary by implementation, so the blueprint associations are the exam-study anchor.

Why must Ethernet cable category and link speed be checked together?

A link can only meet its target speed and distance when the cable, connectors, termination, and interfaces support the same standard. A higher category label does not repair bad installation work.

Which ports map to SQL Server, RDP, and SIP?

SQL Server uses TCP 1433, RDP uses TCP/UDP 3389, and SIP uses 5060/5061. SIP 5061 is commonly associated with TLS-protected signaling.

When should a network use QoS rather than simply adding a VLAN?

Use QoS when traffic needs classification, queuing, or priority under contention. A VLAN separates broadcast domains; it does not by itself reserve bandwidth or prioritize delay-sensitive traffic.

What reliability features does TCP add that UDP does not?

TCP establishes a connection and provides ordered delivery, acknowledgments, retransmission, and flow control. UDP sends independent datagrams with less transport overhead and no delivery guarantee.

CompTIA Network+ N10-009 Flashcards: Concepts, Operations & Troubleshooting

Prepare for CompTIA Network+ N10-009 with 250 original cards covering all five domains through focused recall, configuration choices, operations decisions, security, and troubleshooting scenarios.

Af forfatter Open Study Contributor

Om denne bunke

Study the current CompTIA Network+ N10-009 blueprint with 250 original English flashcards organized to match the official five-domain weighting. The deck moves from networking models, protocols, cloud, addressing, and media into routing, switching, wireless design, physical installation, operations, security, and troubleshooting.

Short recall cards anchor stable facts such as ports and address ranges. Scenario prompts then ask you to choose a configuration, interpret evidence, select a control or tool, and decide the next diagnostic action. Explanations state the answer first and add practical context without imitating multiple-choice exam items.

Scope and technical details were checked against primary references from IANA, the RFC Editor, IEEE, NIST, Microsoft, AWS, and Cisco. The original questions, answers, organization, and generated cover are released under CC0 1.0 to the extent applicable rights exist.

Separate reverse cards appear only when both recall directions are useful. The deck excludes mechanical acronym-to-expansion cards, every possible port-to-protocol reversal, redundant permutations of the same comparison, and hands-on mappings for packet inspection, cable handling, device configuration, or full performance-based practice; those skills need live equipment or labs.

This independent, unofficial study deck is not affiliated with, sponsored by, or endorsed by CompTIA. No real exam questions, answer keys, or verbatim objective text were copied, and the deck does not guarantee a passing result. Check the official N10-009 exam objectives for the authoritative requirements.

Kort i denne bunke

Kort 1
Spørgsmål
At which OSI layer do cables, connectors, radio signals, and raw bits belong?
Svar
Layer 1 — Physical. It moves bits across the medium and defines electrical, optical, radio, connector, and signaling details.
Kort 2
Spørgsmål
A LAN needs forwarding by MAC address, while traffic between IP networks needs forwarding by destination IP. Which appliances fit each job?
Svar
A switch handles the LAN forwarding; a router connects the IP networks. A switch learns Layer 2 MAC addresses, while a router selects Layer 3 paths.
Kort 3
Spørgsmål
What does a virtual private cloud provide?
Svar
An isolated logical network in a cloud. You choose address ranges, subnets, routes, gateways, and traffic controls while logical boundaries separate tenants on shared provider infrastructure.
Kort 4
Spørgsmål
Which well-known ports does FTP use, and why are there two?
Svar
TCP 21 for control and TCP 20 for the traditional active-mode data channel. FTP is unencrypted; secure file transfer normally uses a different protocol such as SFTP.
Kort 5
Spørgsmål
When is single-mode fiber preferred over multimode fiber?
Svar
For longer distances and higher reach. Single-mode uses a smaller core and typically a laser source; multimode is common for shorter links and usually costs less at the endpoints.
Kort 6
Spørgsmål
What is the main operational tradeoff of a star topology?
Svar
A single access link failure usually affects one node, but failure of the central device can affect the whole star. Centralization also makes changes and fault isolation simpler.
Kort 7
Spørgsmål
Which three IPv4 ranges are reserved for private networks by RFC 1918?
Svar
10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Public routers should not treat these as globally routable destination space.
Kort 8
Spørgsmål
How do SDN, SD-WAN, and NFV differ?
Svar
SDN separates programmable control from data forwarding across a network. SD-WAN applies that approach to WAN overlays, using central policy and path conditions to steer traffic across transports. NFV runs network functions as software instead of tying each one to a dedicated appliance.
Kort 9
Spørgsmål
At which OSI layer are Ethernet frames, MAC addresses, and switching decisions handled?
Svar
Layer 2 — Data Link. It packages bits into frames and delivers them across a local link using hardware addresses and link-level control.
Kort 10
Spørgsmål
How does an IPS differ from an IDS in the traffic path?
Svar
An IPS sits inline and can block traffic; an IDS detects and alerts from observed traffic. Inline enforcement adds prevention but also makes availability and tuning more important.
Kort 11
Spørgsmål
In a typical VPC, how do a security group and a network ACL differ?
Svar
A security group filters traffic at a resource interface and is usually stateful; a network ACL filters at the subnet boundary and is stateless. Exact behavior is provider-specific, so verify the platform.
Kort 12
Spørgsmål
Which ports distinguish SSH/SFTP from Telnet?
Svar
SSH and SFTP use TCP 22; Telnet uses TCP 23. SSH encrypts the session, while Telnet sends the session without that protection.
Kort 13
Spørgsmål
What is a direct-attach copper cable in a data-center link?
Svar
A short twinax assembly with transceiver ends fixed to the cable. It is a low-power, low-latency option for nearby switches and servers, but its reach is limited.
Kort 14
Spørgsmål
Why does a spine-and-leaf fabric suit east-west data-center traffic?
Svar
Every leaf connects to every spine, giving a predictable small hop count between endpoints. Adding spines or leaves scales capacity without building a long hierarchical path.
Kort 15
Spørgsmål
A Windows host self-assigns 169.254.24.8/16. What does that suggest?
Svar
APIPA/link-local addressing. The host did not obtain its intended IPv4 configuration, commonly because DHCP was unavailable; the address works only on the local link.
Kort 16
Spørgsmål
How do VXLAN and data center interconnect relate?
Svar
VXLAN carries Layer 2 overlays across an IP underlay; data center interconnect (DCI) links separate data-center sites. A DCI design can extend selected VXLAN segments or exchange routed reachability between sites, but DCI is the inter-site function, not a synonym for VXLAN.
Kort 17
Spørgsmål
At which OSI layer do IP addressing and routing belong?
Svar
Layer 3 — Network. It provides logical addressing and selects paths across interconnected networks.
Kort 18
Spørgsmål
What is the difference between a forward proxy and a reverse proxy?
Svar
A forward proxy acts for clients reaching servers; a reverse proxy acts in front of servers receiving client requests. Both can mediate, filter, cache, or hide the systems behind them.
Kort 19
Spørgsmål
A private cloud subnet needs outbound internet access without accepting unsolicited inbound connections. Which gateway fits?
Svar
A NAT gateway. It translates outbound flows for private addresses and permits return traffic for those flows; an internet gateway alone does not make a private-addressed host reachable.
Kort 20
Spørgsmål
Which well-known ports map to SMTP and DNS?
Svar
SMTP uses TCP 25 for server-to-server mail transfer; DNS uses UDP or TCP 53. DNS commonly uses UDP for ordinary queries and TCP when required by size or operation.
Kort 21
Spørgsmål
Why is plenum-rated cable required in some air-handling spaces?
Svar
Its jacket is designed for stricter flame-spread and smoke requirements. Local fire and building codes decide where it is required; ordinary PVC-jacket cable may not be acceptable there.
Kort 22
Spørgsmål
What are the three layers in the classic three-tier campus design?
Svar
Access, distribution, and core. Access connects endpoints, distribution aggregates access and applies policy, and the core provides fast resilient transport between distribution blocks.
Kort 23
Spørgsmål
What does the IPv4 loopback range test?
Svar
The local host's IP stack. The range is 127.0.0.0/8, with 127.0.0.1 commonly used as localhost; packets never need to reach a physical network.
Kort 24
Spørgsmål
What trust assumption does zero trust architecture reject?
Svar
It rejects implicit trust based only on network location or ownership. Access is evaluated for the user, device, resource, and context, then limited to what policy allows.
Kort 25
Spørgsmål
At which OSI layer do TCP and UDP ports, segmentation, and end-to-end transport belong?
Svar
Layer 4 — Transport. It identifies application endpoints with ports and provides transport behavior such as reliable streams with TCP or datagrams with UDP.
Kort 26
Spørgsmål
How do NAS and SAN present storage differently?
Svar
NAS presents shared files over the network; a SAN presents block storage to hosts. NAS fits file sharing, while SAN-attached storage looks more like a locally attached disk to the server.
Kort 27
Spørgsmål
How do SaaS, PaaS, and IaaS divide customer responsibility?
Svar
SaaS supplies the finished application, PaaS supplies an application platform, and IaaS supplies virtualized compute/network/storage. Customer control and operational responsibility generally increase from SaaS to PaaS to IaaS.
Kort 28
Spørgsmål
Which ports map to DHCP, TFTP, and HTTP?
Svar
DHCP uses UDP 67/68, TFTP uses UDP 69, and HTTP uses TCP 80. DHCP separates server and client ports; TFTP is a simple unauthenticated transfer protocol.
Kort 29
Spørgsmål
What is the practical difference between SFP and QSFP form factors?
Svar
SFP is a small pluggable transceiver family for one link lane; QSFP groups four lanes in a compact module. The suffix and module specification, not the shape alone, determine supported speed and medium.
Kort 30
Spørgsmål
In data-center terminology, how do north-south and east-west traffic differ?
Svar
North-south traffic enters or leaves the data center; east-west traffic moves between internal systems. The distinction helps choose firewall, load-balancing, and fabric capacity placement.
Kort 31
Spørgsmål
A /27 IPv4 subnet has how many addresses and normally how many usable host addresses?
Svar
32 total and 30 normally usable. Five host bits remain, so 2^5 = 32; the network and broadcast addresses are not assigned to ordinary hosts.
Kort 32
Spørgsmål
How does SSE relate to SASE?
Svar
SSE is the cloud-delivered security-services portion; SASE combines those security services with wide-area networking. Implementations vary, but SASE joins connectivity and policy closer to users and resources.
Kort 33
Spørgsmål
At which OSI layer are sessions established, coordinated, and torn down?
Svar
Layer 5 — Session. The conceptual layer manages dialogs and checkpoints between applications, even though real protocol stacks often combine its work with other layers.
Kort 34
Spørgsmål
How do an autonomous access point and a controller-based access point differ?
Svar
An autonomous AP holds its own control configuration; a lightweight AP relies on a controller for centralized policy and coordination. Controller designs simplify consistent changes across many APs.
Kort 35
Spørgsmål
How do public, private, and hybrid cloud deployment models differ?
Svar
Public cloud uses provider-operated shared infrastructure, private cloud is dedicated to one organization, and hybrid connects private and public environments for a combined design.
Kort 36
Spørgsmål
Which ports map to NTP and SNMP?
Svar
NTP uses UDP 123. SNMP queries commonly use UDP 161, while notifications such as traps commonly use UDP 162.
Kort 37
Spørgsmål
Which common fiber connectors are push-pull, small-form-factor latch, bayonet, and multifiber?
Svar
SC is push-pull, LC is the smaller latched connector, ST uses a bayonet twist, and MPO carries multiple fibers in one connector. Always match polish, fiber type, and transceiver requirements too.
Kort 38
Spørgsmål
What makes a hybrid topology different from a mesh topology?
Svar
A hybrid combines two or more topology patterns; a mesh emphasizes multiple interconnections and alternate paths among nodes. A design can be both hybrid and partially meshed.
Kort 39
Spørgsmål
Which first-octet ranges identify the historical IPv4 classes A through E, and how do CIDR and VLSM differ from that model?
Svar
Class A is 1–126 with a default /8, Class B is 128–191 with /16, and Class C is 192–223 with /24; these were classful unicast ranges. Class D is 224–239 for multicast, while Class E is 240–255 and reserved. The 0/8 and 127/8 blocks are special. Modern CIDR uses explicit prefixes, and VLSM lets subnets use different prefix lengths instead of fixed class boundaries.
Kort 40
Spørgsmål
What operational problem does infrastructure as code solve?
Svar
It makes infrastructure definitions repeatable, reviewable, and versioned. Templates and automation reduce manual drift, while source control exposes changes, conflicts, and rollback history.
Kort 41
Spørgsmål
Which OSI layer handles data representation tasks such as format translation, compression, and encryption?
Svar
Layer 6 — Presentation. It describes how applications agree on representation, though modern protocol suites often place these functions inside application protocols or libraries.
Kort 42
Spørgsmål
How do cloud scalability and elasticity differ?
Svar
Scalability is the ability to handle growth by adding resources; elasticity adjusts resources up or down with demand. Elasticity emphasizes timely, often automatic, resizing.
Kort 43
Spørgsmål
Which ports map to LDAP, HTTPS, and SMB?
Svar
LDAP uses TCP/UDP 389, HTTPS uses TCP 443, and SMB commonly uses TCP 445. Encryption depends on the protocol and configuration, not merely on reaching a familiar port.
Kort 44
Spørgsmål
Which connector is typical for Ethernet twisted pair, and which two appear on common coax runs?
Svar
RJ45 is typical for Ethernet twisted pair; F-type and BNC are common coax connectors. RJ11 is smaller and is commonly associated with telephone cabling.
Kort 45
Spørgsmål
At which OSI layer do user-facing network services such as HTTP and DNS sit?
Svar
Layer 7 — Application. It is the top conceptual layer where network services are exposed to applications and users.
Kort 46
Spørgsmål
Why can a content delivery network reduce page latency?
Svar
It serves cacheable content from distributed edge locations closer to users. The shorter path and offloaded origin reduce delay and origin demand when caching rules fit the content.
Kort 47
Spørgsmål
Which ports map to Syslog, secure mail submission, and LDAPS in the N10-009 blueprint?
Svar
Syslog uses 514, secure SMTP submission uses 587, and LDAPS uses 636. Transport details can vary by implementation, so the blueprint associations are the exam-study anchor.
Kort 48
Spørgsmål
Why must Ethernet cable category and link speed be checked together?
Svar
A link can only meet its target speed and distance when the cable, connectors, termination, and interfaces support the same standard. A higher category label does not repair bad installation work.
Kort 49
Spørgsmål
Which ports map to SQL Server, RDP, and SIP?
Svar
SQL Server uses TCP 1433, RDP uses TCP/UDP 3389, and SIP uses 5060/5061. SIP 5061 is commonly associated with TLS-protected signaling.
Kort 50
Spørgsmål
When should a network use QoS rather than simply adding a VLAN?
Svar
Use QoS when traffic needs classification, queuing, or priority under contention. A VLAN separates broadcast domains; it does not by itself reserve bandwidth or prioritize delay-sensitive traffic.
Kort 51
Spørgsmål
What reliability features does TCP add that UDP does not?
Svar
TCP establishes a connection and provides ordered delivery, acknowledgments, retransmission, and flow control. UDP sends independent datagrams with less transport overhead and no delivery guarantee.
Kort 52
Spørgsmål
What does ICMP provide to IP networks?
Svar
Control and error-reporting messages, including echo request/reply used by ping. ICMP supports diagnosis and network operation; it is not an application data transport like TCP or UDP.
Kort 53
Spørgsmål
What problem does GRE solve, and what does it not provide by itself?
Svar
GRE encapsulates one network-layer protocol inside another to form a tunnel. It does not provide encryption or integrity by itself, so protected designs pair it with a security mechanism such as IPsec.
Kort 54
Spørgsmål
In IPsec, what are the jobs of AH, ESP, and IKE?
Svar
AH authenticates packet data without encrypting the payload; ESP can provide confidentiality plus integrity/authentication; IKE negotiates security associations and keys.
Kort 55
Spørgsmål
How do unicast, multicast, broadcast, and anycast choose recipients?
Svar
Unicast targets one interface, multicast targets subscribed group members, broadcast targets the local IPv4 broadcast domain, and anycast reaches one member of a group—normally the closest by routing.
Kort 56
Spørgsmål
What happens when a router reduces an IP packet's TTL or hop limit to zero?
Svar
The router discards the packet and normally sends an ICMP time-exceeded message. This prevents a routing loop from circulating a packet forever and enables traceroute-style path discovery.
Kort 57
Spørgsmål
Why does IPv6 reduce pressure from IPv4 address exhaustion?
Svar
IPv6 expands addresses from 32 bits to 128 bits, providing vastly more unique address space. It also supports simpler autoconfiguration, but migration still requires routing, security, and application readiness.
Kort 58
Spørgsmål
How do dual stack, tunneling, and NAT64 help an IPv6 transition?
Svar
Dual stack runs IPv4 and IPv6 together, tunneling carries one protocol through the other network, and NAT64 translates between IPv6 clients and IPv4 services. Each solves a different compatibility gap.
Kort 59
Spørgsmål
When is a static route more suitable than a dynamic routing protocol?
Svar
When the path is simple, stable, and intentionally controlled, such as a default route from a small branch. Static routes add no routing-protocol traffic but require manual updates when topology changes.
Kort 60
Spørgsmål
What problem does a VLAN solve on a switched network?
Svar
It creates a separate Layer 2 broadcast domain on shared switching hardware. Devices in different VLANs need Layer 3 routing to communicate, even if they use the same physical switch.
Kort 61
Spørgsmål
What tradeoff comes with using a wider Wi-Fi channel?
Svar
A wider channel can carry more data under good conditions but consumes more spectrum and leaves fewer nonoverlapping choices. In a crowded area, narrower channels can improve reuse and stability.
Kort 62
Spørgsmål
How do an MDF and an IDF differ in structured cabling?
Svar
The main distribution frame is the building's primary cross-connect and service-entry area; an intermediate distribution frame serves a floor or zone and uplinks to the MDF.
Kort 63
Spørgsmål
What do RIP, OSPF, EIGRP, and BGP broadly represent?
Svar
RIP is distance-vector, OSPF is link-state, EIGRP is an advanced distance-vector protocol, and BGP is a path-vector interdomain protocol. Their design scope and route-selection inputs differ.
Kort 64
Spørgsmål
What is a switched virtual interface used for?
Svar
An SVI gives a VLAN a Layer 3 interface on a multilayer switch. It can be the hosts' default gateway and route traffic between VLANs when routing is enabled.
Kort 65
Spørgsmål
How should 2.4 GHz, 5 GHz, and 6 GHz influence Wi-Fi design?
Svar
2.4 GHz usually reaches farther but has less clean spectrum; 5 GHz offers more channels and capacity with shorter reach; 6 GHz adds cleaner spectrum for supported clients but requires compatible radios and security settings.
Kort 66
Spørgsmål
What does one rack unit measure?
Svar
1U is 1.75 inches, or 44.45 millimeters, of vertical rack space. A 2U device occupies twice that height, but depth, power, cooling, and rail compatibility still need separate checks.
Kort 67
Spørgsmål
When several routes match a destination, which prefix does the router prefer first?
Svar
The longest matching prefix—the most specific route. Only after comparing equally specific candidates do protocol preference and metric normally decide among them.
Kort 68
Spørgsmål
What is the native VLAN on an 802.1Q trunk?
Svar
It is the VLAN associated with untagged frames on that trunk. Both ends should agree on it; a mismatch can leak traffic into the wrong broadcast domain and create confusing control-plane behavior.
Kort 69
Spørgsmål
What does band steering try to accomplish on a dual- or tri-band WLAN?
Svar
It encourages capable clients toward the preferred band, often 5 or 6 GHz, to reduce 2.4 GHz congestion. The client still influences the final association decision.
Kort 70
Spørgsmål
Why should network racks use a planned front-to-back airflow path?
Svar
It keeps cool intake air separate from hot exhaust and reduces recirculation. Correct device orientation, blanking panels, temperature monitoring, and unobstructed aisles all support the airflow plan.
Kort 71
Spørgsmål
What does administrative distance compare on a router?
Svar
The trust preference of routes learned from different sources. Lower values are normally preferred, but the exact values are vendor-specific and are considered only after longest-prefix matching.
Kort 72
Spørgsmål
Why assign voice devices to a dedicated voice VLAN?
Svar
It separates voice traffic for policy, addressing, QoS marking, and security while allowing a phone and attached workstation to share one switch port. The switch and phone must agree on the configuration.
Kort 73
Spørgsmål
How do SSID, BSSID, and ESS differ?
Svar
The SSID is the human-facing wireless network name; the BSSID identifies a specific basic service set, commonly an AP radio; an ESS joins multiple cells under one logical WLAN for roaming.
Kort 74
Spørgsmål
Why terminate horizontal cabling on a patch panel instead of directly on switches?
Svar
Permanent cable stays fixed and labeled while short patch cords handle changes. This reduces wear on building cable and makes tracing, rearrangement, and documentation safer.
Kort 75
Spørgsmål
What does a routing metric decide?
Svar
It ranks candidate routes learned by the same routing process, using inputs such as cost, bandwidth, delay, or hop count. Lower is commonly better, but interpretation depends on the protocol.
Kort 76
Spørgsmål
What information does an 802.1Q tag add to an Ethernet frame?
Svar
It carries VLAN identification and priority information so multiple VLANs can share a trunk. The tag changes the frame format, so trunk peers must support and consistently configure it.
Kort 77
Spørgsmål
How does an infrastructure WLAN differ from an ad hoc WLAN and a mesh?
Svar
Infrastructure clients associate through APs; ad hoc peers connect directly; a mesh uses wireless links among infrastructure nodes to extend backhaul or coverage. Each topology has different scale and management tradeoffs.
Kort 78
Spørgsmål
How do a UPS and a PDU serve different rack-power needs?
Svar
A UPS provides temporary conditioned power during an outage; a PDU distributes available power to rack equipment. A metered or switched PDU may add monitoring or remote outlet control but is not a battery backup.
Kort 79
Spørgsmål
How do static NAT and port address translation differ?
Svar
Static NAT keeps a fixed one-to-one address mapping; PAT lets many inside flows share a public address by distinguishing them with transport ports. PAT conserves addresses but complicates unsolicited inbound access.
Kort 80
Spørgsmål
What does link aggregation provide, and what must it not be mistaken for?
Svar
It bundles compatible physical links into one logical link for added capacity and resilience. A single flow may still use one member, and both ends need a matching aggregation configuration.
Kort 81
Spørgsmål
When is a point-to-point wireless link preferable to a broad coverage cell?
Svar
When two known sites need a focused bridge. Directional antennas can concentrate energy along the path, improving reach and reducing spill, but line-of-sight and Fresnel-zone clearance matter.
Kort 82
Spørgsmål
What must be checked before adding a high-power device to a rack PDU?
Svar
Input voltage, circuit and PDU capacity, connector type, redundancy plan, and the device's actual load. Keep continuous load within applicable electrical limits and avoid defeating redundant power paths.
Kort 83
Spørgsmål
What problem does a first-hop redundancy protocol solve?
Svar
It lets multiple routers present a shared virtual gateway address to hosts. If the active forwarder fails, another router can assume the virtual role without changing endpoint default gateways.
Kort 84
Spørgsmål
Why should Ethernet speed and duplex normally be configured consistently at both link ends?
Svar
A mismatch can cause poor throughput, late collisions, and interface errors even when the link appears up. Autonegotiation on both ends is usually safest unless the design explicitly requires matching manual settings.
Kort 85
Spørgsmål
How do WPA2 and WPA3 improve a WLAN compared with an open network?
Svar
They add authenticated encryption. WPA3 strengthens password-based authentication with SAE and requires protected management frames in standard deployments; client and AP compatibility still determines the usable mode.
Kort 86
Spørgsmål
Which physical controls protect a telecommunications room beyond its network configuration?
Svar
Locked access, cameras or access logs, fire protection, temperature and humidity monitoring, clean power, and leak detection. Physical and environmental failures bypass logical controls.
Kort 87
Spørgsmål
Why is BGP normally used between autonomous systems rather than as a small LAN's default routing protocol?
Svar
BGP exchanges reachability and path attributes between independently administered networks. It emphasizes policy and Internet-scale routing, which is unnecessary complexity for a small internal topology.
Kort 88
Spørgsmål
What failure does Spanning Tree Protocol prevent on redundant switched links?
Svar
Layer 2 loops. STP builds a loop-free logical tree and blocks redundant paths until needed, preventing broadcast storms and unstable MAC-table learning.
Kort 89
Spørgsmål
What should a guest WLAN isolate even when it uses a captive portal?
Svar
Guest clients from internal resources and usually from one another. A captive portal handles access or terms; it is not a substitute for segmentation, filtering, and protected management traffic.
Kort 90
Spørgsmål
What makes OSPF a link-state routing protocol?
Svar
Routers describe links, flood that topology information within an area, build a common link-state database, and calculate shortest paths. This differs from advertising only a distance and direction to routes.
Kort 91
Spørgsmål
Why can enabling jumbo frames on only part of a path break traffic?
Svar
Every relevant interface must support a compatible MTU. An oversized frame can be dropped where the path narrows, causing loss that may affect only larger packets and therefore look intermittent.
Kort 92
Spørgsmål
When is WPA-Enterprise preferred over a pre-shared key?
Svar
When users or devices need individual credentials, centralized policy, and revocation without changing one shared secret. It normally combines 802.1X/EAP with an authentication service such as RADIUS.
Kort 93
Spørgsmål
What operational tradeoff accompanies EIGRP in a multivendor network?
Svar
EIGRP can converge efficiently and use composite metrics, but support and behavior must be verified across the actual vendors. OSPF is a more common open-standard choice for broad interoperability.
Kort 94
Spørgsmål
Two departments share switches but must have separate broadcasts and policy. What should be configured first?
Svar
Separate VLANs for the departments, then Layer 3 gateways and explicit inter-VLAN policy where communication is required. Physical separation is not necessary for basic broadcast isolation.
Kort 95
Spørgsmål
How do omnidirectional and directional antennas change a wireless design?
Svar
An omnidirectional antenna spreads coverage broadly around it; a directional antenna concentrates energy into a narrower area. Placement, gain, polarization, and local power limits all affect the usable cell.
Kort 96
Spørgsmål
A routing table has 10.0.0.0/8, 10.4.0.0/16, and a default route. Which entry handles 10.4.7.9?
Svar
10.4.0.0/16 because it is the longest matching prefix. The /8 also matches, but the more specific /16 wins; the default is used only when no more specific entry matches.
Kort 97
Spørgsmål
Hosts on one side of a trunk appear in the wrong VLAN only for untagged traffic. What mismatch is most likely?
Svar
A native VLAN mismatch. Check both trunk endpoints, allowed VLANs, and whether the design expects untagged frames before changing the configuration.
Kort 98
Spørgsmål
When does a controller-based WLAN offer more value than autonomous APs?
Svar
When many APs need consistent configuration, radio coordination, roaming support, monitoring, and centralized policy. A small isolated site may accept autonomous management to avoid controller complexity.
Kort 99
Spørgsmål
Why configure a default static route at a single-exit branch?
Svar
It directs all otherwise unknown destinations toward the upstream router with one simple entry. The route should be monitored or paired with failover logic if the branch has another possible exit.
Kort 100
Spørgsmål
A link aggregation loses one member but stays up. What should happen to traffic and capacity?
Svar
Traffic should be redistributed across the remaining members, while total available capacity falls. Verify the bundle state at both ends because a one-sided member can create loss or an unintended separate path.
Kort 101
Spørgsmål
Why are channels 1, 6, and 11 commonly chosen for 20 MHz 2.4 GHz Wi-Fi in many regulatory domains?
Svar
Their channel centers avoid overlap under the common 20 MHz plan, improving reuse compared with adjacent channels. Confirm local regulations and the actual channel width before applying that rule.
Kort 102
Spørgsmål
What does router-on-a-stick require between a switch and router?
Svar
An 802.1Q trunk to router subinterfaces, with one subinterface and gateway address per VLAN. The single physical link can become a bandwidth and availability bottleneck.
Kort 103
Spørgsmål
How does STP choose the root bridge and a switch's preferred path toward it?
Svar
The lowest bridge ID becomes root; non-root switches select the path with the lowest root path cost, then use tie-breakers if needed. Intentional bridge priorities make the topology predictable.
Kort 104
Spørgsmål
A 6 GHz-capable WLAN has excellent spectrum but older clients cannot see it. What is the correct design response?
Svar
Keep a compatible 2.4 or 5 GHz service for older clients and use 6 GHz for capable devices. Do not weaken the 6 GHz security model merely to support legacy hardware.
Kort 105
Spørgsmål
A router learns the same prefix from OSPF and a static route. Which two controls decide the winner after prefix length?
Svar
Administrative distance chooses between route sources; the relevant metric chooses among comparable routes within a source. Exact preference values and equal-cost behavior depend on the platform.
Kort 106
Spørgsmål
Large storage transfers fail across one switch while small pings work. Which switching setting deserves comparison end to end?
Svar
The MTU/jumbo-frame setting. Compare host, switch, routed interface, and tunnel overhead across the full path; a single smaller segment can drop only the larger frames.
Kort 107
Spørgsmål
What WLAN design choices support roaming across several access points?
Svar
Consistent SSID and security policy, adequate overlapping coverage, noninterfering channels, coordinated AP power, and a compatible distribution network. The client ultimately decides when to roam.
Kort 108
Spørgsmål
A crowded office has many neighboring APs and unstable Wi-Fi. Why might reducing channel width help?
Svar
Narrower channels create more reusable channel choices and reduce overlap. Peak speed per client may fall, but total reliability and airtime efficiency can improve in a dense deployment.
Kort 109
Spørgsmål
When should a network document use a logical diagram instead of a physical diagram?
Svar
Use a logical diagram for subnets, VLANs, routing, trust zones, and data paths; use a physical diagram for devices, ports, cables, rooms, and rack placement. Mature documentation often keeps both linked.
Kort 110
Spørgsmål
How do SNMP polling and an SNMP trap differ?
Svar
Polling is a manager's scheduled request for device data; a trap is an unsolicited device notification. A MIB describes managed objects; SNMPv3 can authenticate and protect messages, unlike community-string-based SNMPv2c.
Kort 111
Spørgsmål
How do recovery point objective and recovery time objective differ?
Svar
RPO is the maximum acceptable data-loss interval; RTO is the target time to restore service. A four-hour RPO concerns data age, while a one-hour RTO concerns outage duration.
Kort 112
Spørgsmål
What is the difference between a DHCP scope and a reservation?
Svar
A scope defines the address pool and options for a subnet; a reservation maps a known client identifier to a chosen address. The reserved address should not also be freely offered to other clients.
Kort 113
Spørgsmål
When is a site-to-site VPN preferable to a client VPN?
Svar
Use site-to-site for persistent connectivity between networks through gateways; use a client VPN for individual endpoints. A full tunnel carries all client traffic, a split tunnel carries selected routes, and clientless access commonly exposes specific web applications.
Kort 114
Spørgsmål
What does a rack diagram answer that a cable map may not?
Svar
A rack diagram shows device placement, rack units, and often power layout; a cable map traces endpoints, ports, media, and paths. Together they reduce search time during changes and failures.
Kort 115
Spørgsmål
When is flow telemetry more useful than a full packet capture?
Svar
Flow records are better for broad, longer-term visibility into who talked to whom, how much, and when. Packet capture is better for protocol and payload detail but consumes more storage and may contain sensitive data.
Kort 116
Spørgsmål
How do MTBF and MTTR describe reliability?
Svar
Mean time between failures estimates how long a repairable system operates between failures; mean time to repair or restore estimates recovery duration. Higher MTBF and lower MTTR generally improve availability.
Kort 117
Spørgsmål
Why configure both DHCP exclusions and lease duration deliberately?
Svar
Exclusions keep infrastructure or statically assigned addresses out of the dynamic pool; lease duration controls how long clients retain assignments. Short leases recycle addresses faster but increase DHCP activity.
Kort 118
Spørgsmål
What is the operational tradeoff between SSH and a device's web GUI?
Svar
SSH is efficient, scriptable command-line access; a GUI can make discovery and complex views easier. Both require protected management paths, strong authentication, and change logging.
Kort 119
Spørgsmål
Which fields make a network asset inventory useful during an incident?
Svar
At minimum: unique asset ID, role, owner, location, model, serial number, software version, management address, support status, and dependencies. Accurate ownership and location shorten escalation and replacement time.
Kort 120
Spørgsmål
Why establish a normal performance baseline before setting alerts?
Svar
A baseline shows expected patterns by time and workload, so thresholds can detect meaningful deviation. Without it, alerts tend to miss gradual degradation or fire on ordinary peaks.
Kort 121
Spørgsmål
How do cold, warm, and hot recovery sites differ?
Svar
A cold site supplies space and basics, a warm site has partial systems or replicated resources, and a hot site is kept near ready for rapid failover. Faster recovery normally costs more.
Kort 122
Spørgsmål
Why is a DHCP relay needed when clients and the DHCP server are on different subnets?
Svar
Initial client broadcasts do not cross routers. The relay receives the local broadcast and forwards the request to the server with subnet context so the server can choose the correct scope.
Kort 123
Spørgsmål
What makes an API useful for network-device management?
Svar
It provides structured, automatable operations for reading state and applying changes. Safe use requires authentication, authorization, version awareness, idempotency where supported, error handling, and audit records.
Kort 124
Spørgsmål
What should IP address management record beyond a list of assigned addresses?
Svar
Subnets, prefixes, VLANs, gateways, reservations, DNS/DHCP relationships, owners, locations, status, and allocation history. IPAM helps prevent overlap and exposes stale assignments.
Kort 125
Spørgsmål
Why centralize network logs in a SIEM or log platform?
Svar
Centralization preserves searchable history and correlates events across devices, identities, and time. It only works well when clocks, source identities, retention, parsing, and access controls are reliable.
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Kort 126
Spørgsmål
What distinguishes high availability from disaster recovery?
Svar
High availability reduces interruption through redundant components and automatic failover; disaster recovery restores service after a larger disruption. Active-active nodes share work, while active-passive designs keep a standby; neither replaces tested recovery.
Kort 127
Spørgsmål
How does IPv6 SLAAC give a host an address?
Svar
The host uses router advertisements for prefix and network information, then forms an address and checks uniqueness. SLAAC does not necessarily supply every setting an organization wants, so DHCPv6 or other mechanisms may complement it.
Kort 128
Spørgsmål
How do local console access and out-of-band management differ?
Svar
A local console connects directly to the device and usually requires someone on-site. Out-of-band management reaches a console server or dedicated management interface through a separate management network, so remote access can survive a production-path failure. Both paths still need strict access controls.
Kort 129
Spørgsmål
What should a network service-level agreement make measurable?
Svar
Scope, availability or performance targets, measurement method, support hours, response and restoration targets, exclusions, escalation, reporting, and remedies. Vague promises are difficult to operate or enforce.
Kort 130
Spørgsmål
Why configure a switch port mirror during packet analysis?
Svar
It copies selected ingress or egress traffic to an analyzer without placing the analyzer inline. Oversubscription, incorrect direction, or missing VLANs can make the capture incomplete.
Kort 131
Spørgsmål
What does a tabletop disaster-recovery exercise test?
Svar
People walk through a realistic incident to expose unclear roles, missing contacts, dependency gaps, and decision bottlenecks. It validates the plan's logic but does not prove that systems can actually fail over.
Kort 132
Spørgsmål
What do the common DNS records A, AAAA, CNAME, MX, TXT, NS, and PTR store?
Svar
A stores an IPv4 address; AAAA stores IPv6; CNAME aliases another name; MX names a mail exchanger; TXT stores text used for policies or verification; NS names an authoritative server for a zone; and PTR maps an address-domain entry back to a name.
Kort 133
Spørgsmål
Why route administrator access through a jump box?
Svar
It concentrates entry into a hardened, monitored system with controlled tools and network reach. The jump box becomes high value, so patching, MFA, session logging, and limited privileges are essential.
Kort 134
Spørgsmål
Why perform both predictive and post-deployment wireless surveys?
Svar
Predictive work estimates AP placement from models; the post-deployment survey measures real coverage, interference, and capacity. Walls, occupants, neighboring networks, and device behavior make field validation necessary.
Kort 135
Spørgsmål
Which environmental readings should network monitoring collect in equipment spaces?
Svar
Temperature, humidity, power state and load, UPS health, fan status, smoke or fire signals, and water or door sensors where relevant. Thresholds should reflect the equipment and facility design.
Kort 136
Spørgsmål
Why is a successful backup job not enough evidence of recoverability?
Svar
A backup can be incomplete, corrupted, inaccessible, or too slow to restore. Periodic restore tests verify data, credentials, procedures, dependencies, and whether recovery meets RPO and RTO.
Kort 137
Spørgsmål
How do forward and reverse DNS zones differ, and how do primary, secondary, authoritative, and recursive roles fit?
Svar
A forward zone maps names to data such as addresses; a reverse zone uses PTR records to map addresses back to names. A primary holds the locally maintained zone data, while a secondary receives its copy through zone transfer; both can answer authoritatively for that zone. A recursive resolver follows referrals or uses cache, so its reply to a client is normally non-authoritative.
Kort 138
Spørgsmål
What is the operational difference between end-of-life and end-of-support?
Svar
End-of-life marks a product's retirement from the vendor lifecycle; end-of-support marks when fixes or assistance stop. Exact vendor definitions vary, so record the dates and replacement risk for each asset.
Kort 139
Spørgsmål
How should alert thresholds avoid both missed incidents and alert fatigue?
Svar
Base them on normal behavior, business impact, duration, and rate of change; use warning and critical levels plus suppression for known maintenance. Revisit thresholds after topology or workload changes.
Kort 140
Spørgsmål
What must be planned before relying on a generator for network continuity?
Svar
Fuel, automatic transfer, startup time, load capacity, maintenance, exhaust and safety, refueling access, and UPS runtime until generation stabilizes. Regular load testing reveals failures that idle checks miss.
Kort 141
Spørgsmål
What protection does DNSSEC add, and what does it not add?
Svar
DNSSEC lets resolvers validate that signed DNS data is authentic and unmodified. It does not encrypt the query or hide the requested name; encrypted transports address that separate concern.
Kort 142
Spørgsmål
What should a network change record contain before implementation?
Svar
Purpose, owner, affected systems, risk and impact, prerequisites, implementation steps, validation, maintenance window, communications, approvals, and rollback criteria. Afterwards, record the observed result.
Kort 143
Spørgsmål
Why can a device show uptime while its service is unavailable?
Svar
Uptime only says the device or process has remained running. Availability includes whether users can successfully reach and use the service across all required dependencies.
Kort 144
Spørgsmål
Why does disaster recovery require role succession and more than one trained operator?
Svar
The primary owner may be unavailable during the event. Named backups, accessible runbooks, delegated authority, and practice reduce key-person risk and prevent recovery from waiting on one individual.
Kort 145
Spørgsmål
How do DNS over HTTPS and DNS over TLS protect lookups?
Svar
Both encrypt DNS between a client and a resolver: DoH uses HTTPS, while DoT uses a dedicated TLS service. Neither guarantees that the resolver's upstream data is correct; DNSSEC validation addresses authenticity.
Kort 146
Spørgsmål
Why keep known-good network configuration backups outside the device?
Svar
A device failure, compromise, or bad change can destroy the running configuration. Versioned external copies support comparison, replacement, rollback, and evidence of who changed what.
Kort 147
Spørgsmål
How do ad hoc and scheduled network discovery differ?
Svar
Ad hoc discovery is an authorized, on-demand scan for an immediate question. Scheduled discovery repeats automatically at defined intervals to keep inventory and topology data current. Either approach needs a clear scope and scan-load limits.
Kort 148
Spørgsmål
What is a golden configuration, and how is it different from a performance baseline?
Svar
A golden configuration is an approved desired device state; a performance baseline records normal measured behavior. One detects configuration drift, while the other helps spot operational deviation.
Kort 149
Spørgsmål
Which wireless metrics reveal congestion even when signal strength is good?
Svar
Channel utilization, retransmissions, noise, error rate, client count, airtime consumption, and latency. A strong signal does not guarantee free airtime or low interference.
Kort 150
Spørgsmål
What should be documented when a network device is decommissioned?
Svar
Approval, service dependencies removed, configuration and logs retained as required, data sanitization, licenses, inventory status, IP/DNS updates, physical disposition, and the date and responsible owner.
Kort 151
Spørgsmål
Why is synchronized time essential when correlating Syslog events?
Svar
Investigators need a trustworthy sequence across devices. If clocks or time zones differ, related events appear out of order; synchronized sources and normalized timestamps make correlation defensible.
Kort 152
Spørgsmål
How should configuration drift be handled after it is detected?
Svar
Compare the live state with the approved source, identify whether the difference was authorized, assess impact, then reconcile through change control. Blindly overwriting drift can remove a necessary emergency change.
Kort 153
Spørgsmål
When is a network TAP or packet broker preferable to a simple switch mirror?
Svar
For persistent, higher-fidelity visibility or aggregation across links. TAPs and brokers can reduce dependence on switch resources, while a mirror port is simpler for bounded troubleshooting.
Kort 154
Spørgsmål
A technician moves a patch cord during an outage. Which documentation must be updated before the work is considered complete?
Svar
The affected port and cable map, device or rack diagram if topology changed, labels, change record, and any IPAM or inventory relationship. Physical reality and documentation must agree for the next incident.
Kort 155
Spørgsmål
How do NTP, PTP, and Network Time Security address time synchronization?
Svar
NTP provides general network time, PTP targets much tighter synchronization on suitable networks, and NTS adds cryptographic protection to NTP exchanges. Choose precision and security for the actual use case.
Kort 156
Spørgsmål
What do confidentiality, integrity, and availability protect?
Svar
Confidentiality limits disclosure, integrity protects correctness and authorized change, and availability keeps systems usable when needed. Security decisions often trade among all three.
Kort 157
Spørgsmål
How does a distributed denial-of-service attack differ from a single-source DoS attack?
Svar
A DDoS attack coordinates traffic or work from many sources, making simple source blocking less effective. Both aim to exhaust capacity or state so legitimate users lose service.
Kort 158
Spørgsmål
Which first hardening steps reduce a new network device's attack surface?
Svar
Change default credentials, patch supported software, disable unused services and ports, restrict management access, use secure protocols, enable logging and time sync, and back up the approved configuration.
Kort 159
Spørgsmål
How do data at rest, in transit, and in use differ?
Svar
At rest is stored, in transit is moving between systems, and in use is actively processed. Disk encryption, transport encryption, and runtime access controls protect different states.
Kort 160
Spørgsmål
What role does a certificate authority play in PKI?
Svar
It signs certificates that bind public keys to identities under defined validation rules. Clients must trust the issuing chain and still check name, validity period, usage, and revocation status.
Kort 161
Spørgsmål
How can an attacker attempt VLAN hopping?
Svar
By abusing trunk negotiation or crafted tagging to reach a VLAN not intended for the access port. Disable unnecessary trunk negotiation, explicitly configure access ports, restrict allowed VLANs, and choose native VLANs carefully.
Kort 162
Spørgsmål
How do NAC and 802.1X work together at a network edge?
Svar
802.1X controls port access using a supplicant, authenticator, and authentication server; NAC applies broader identity, device posture, and access policy. Failed endpoints may be denied or placed in a restricted segment.
Kort 163
Spørgsmål
Why is MFA stronger than a password alone?
Svar
It requires evidence from different factor types, such as knowledge plus possession or inherence. Two passwords are not two factors, and phishing-resistant methods provide stronger protection than easily relayed codes.
Kort 164
Spørgsmål
What benefit does single sign-on provide, and what new risk does it concentrate?
Svar
SSO reduces repeated logins and centralizes identity policy, but compromise or outage of the identity provider can affect many applications. Strong MFA, availability, logging, and limited sessions matter.
Kort 165
Spørgsmål
What happens during a MAC flooding attack against a switch?
Svar
The attacker sends many source MAC addresses to pressure the forwarding table. If the switch begins flooding unknown unicast frames, traffic may be exposed or service degraded; port security and rate controls help.
Kort 166
Spørgsmål
What can switch port security enforce?
Svar
It can limit which or how many MAC addresses appear on an access port and choose an action for violations. It reduces casual misuse but does not authenticate a human or prove a device is trustworthy.
Kort 167
Spørgsmål
When is TACACS+ often preferred to RADIUS for device administration?
Svar
When granular command authorization and separate accounting for administrator actions are important. RADIUS is widely used for network access; exact encryption, transport, and vendor support should be verified.
Kort 168
Spørgsmål
How do LDAP and SAML serve different identity roles?
Svar
LDAP accesses directory data and authentication services; SAML exchanges signed assertions for federated web sign-on. They can coexist, with an identity provider reading a directory before issuing an assertion.
Kort 169
Spørgsmål
How does ARP spoofing enable an on-path position on a LAN?
Svar
Forged ARP messages associate the attacker's MAC address with another host's IPv4 address, often the gateway. Victims then send frames through the attacker, who can relay, inspect, modify, or drop them.
Kort 170
Spørgsmål
Why is MAC filtering a weak primary access control?
Svar
MAC addresses are visible on the local medium and can be spoofed. Filtering can support inventory or basic policy, but authenticated access such as 802.1X provides stronger identity evidence.
Kort 171
Spørgsmål
How do least privilege and role-based access control reinforce each other?
Svar
Least privilege limits access to what work requires; RBAC grants permissions through defined job roles. Roles should be narrow, reviewed, time-bounded when practical, and separated for conflicting duties.
Kort 172
Spørgsmål
How does TOTP differ from time-of-day access rules and geofencing?
Svar
A time-based one-time password (TOTP) derives a short-lived authentication code from a shared secret and the current time. Time-of-day rules and geofencing restrict access by schedule or location; they add context but do not prove identity. TOTP only adds another authentication factor when it is paired with a different factor.
Kort 173
Spørgsmål
What is DNS cache poisoning?
Svar
It inserts a false DNS answer into a resolver's cache so later clients are directed incorrectly. Source validation, randomization, secure resolver operation, and DNSSEC validation reduce the risk.
Kort 174
Spørgsmål
What makes encryption-key management as important as the cipher?
Svar
Keys must be generated, stored, distributed, rotated, revoked, recovered, and destroyed securely. A strong algorithm cannot protect data if keys are exposed, reused carelessly, or unavailable during recovery.
Kort 175
Spørgsmål
How do threat, vulnerability, exploit, and risk relate?
Svar
A threat could cause harm, a vulnerability is a weakness, an exploit uses a weakness, and risk combines likelihood with impact. Controls reduce likelihood, impact, or both.
Kort 176
Spørgsmål
Why do data locality and compliance affect network architecture?
Svar
Rules or contracts may restrict where data is stored, processed, inspected, or transferred. Network paths, cloud regions, logging, encryption, retention, and third parties must match those obligations.
Kort 177
Spørgsmål
What symptoms suggest a rogue DHCP server?
Svar
Clients receive an unexpected gateway, DNS server, subnet, or lease and may lose access or route through an attacker. DHCP snooping, switch-port tracing, and comparison with the authorized scope help isolate it.
Kort 178
Spørgsmål
What is the difference between a standard ACL and application-aware filtering?
Svar
A standard IPv4 ACL matches only the source IP address. An extended ACL can also match the destination address, IP protocol, and TCP or UDP ports. Application-aware filtering uses higher-layer context to identify applications, even when ports alone are ambiguous. Rule order and inbound or outbound direction still determine what the policy actually permits or denies.
Kort 179
Spørgsmål
How does network segmentation reduce the blast radius of a compromise?
Svar
It separates systems into policy boundaries and permits only required flows between them. Effective segmentation needs enforcement, logging, route control, and tests that prove unintended paths are closed.
Kort 180
Spørgsmål
How does an evil twin differ from any unauthorized access point?
Svar
An evil twin impersonates a trusted WLAN to lure clients; a rogue AP is any unauthorized AP, even without impersonation. Validate BSSIDs, certificates, location, and wired switch connections before responding.
Kort 181
Spørgsmål
What can URL and content filtering enforce that an IP-only rule cannot?
Svar
Policy based on requested domains, categories, or inspected application content. Encryption and privacy constraints can limit visibility, so filtering must be designed with endpoint, DNS, proxy, and legal controls.
Kort 182
Spørgsmål
Which physical controls deter or reveal unauthorized entry to a network room?
Svar
Locks or badge access, visitor controls, cameras, door alarms, tamper seals, secure racks, and access logs. Controls should also preserve safe emergency access.
Kort 183
Spørgsmål
What can an on-path attacker do even without fully taking a service offline?
Svar
Observe, delay, replay, modify, redirect, or selectively drop traffic. Mutual authentication, authenticated encryption, secure name resolution, and path monitoring limit the opportunity and impact.
Kort 184
Spørgsmål
How should trusted, untrusted, and management security zones differ?
Svar
Each zone should have explicit allowed flows based on function and risk. The untrusted zone receives minimal access, trusted zones are not implicitly unrestricted, and management paths are tightly limited and monitored.
Kort 185
Spørgsmål
What is the defensive purpose of a honeypot?
Svar
It is a decoy intended to attract and observe suspicious activity, creating high-signal alerts and intelligence. It must be isolated and monitored so it cannot become a pivot into production.
Kort 186
Spørgsmål
Why can phishing bypass otherwise strong network controls?
Svar
It manipulates a person into granting access, revealing credentials, or running content through an allowed path. Training, phishing-resistant MFA, filtering, least privilege, and clear reporting reduce the risk.
Kort 187
Spørgsmål
What is the purpose of a screened subnet, often called a DMZ?
Svar
It places public-facing services in a separate policy zone between untrusted and internal networks. Compromise of an exposed service should not grant direct access to protected internal systems.
Kort 188
Spørgsmål
Why use defense in depth instead of relying on one security appliance?
Svar
Multiple independent controls across identity, endpoint, network, application, data, and recovery reduce single-point failure. Layers should address different attack stages and produce usable evidence.
Kort 189
Spørgsmål
How can malware create a network symptom rather than only an endpoint symptom?
Svar
It may scan, beacon, exfiltrate, spread, consume bandwidth, alter DNS or proxy settings, or launch attacks. Correlate endpoint alerts with flows, DNS, authentication, and packet evidence.
Kort 190
Spørgsmål
A firewall rule allows any source to a management port. What is the safer replacement?
Svar
Allow only approved administration sources through the protected management path, require strong authentication, log access, and deny other traffic. Preserve tested emergency access without exposing the port broadly.
Kort 191
Spørgsmål
What should a technician collect before proposing a cause for a network problem?
Svar
Symptoms, scope, timing, recent changes, affected and unaffected users, error messages, topology, baselines, and reproduction steps. Start by identifying the problem without assuming the first report is the root cause.
Kort 192
Spørgsmål
A newly patched Ethernet port has no link. Which physical checks come before changing switch software?
Svar
Confirm the correct ports and cable type, seat both connectors, inspect damage and link lights, test the patch cord, and compare speed/media support. Replace one known-bad or uncertain component at a time.
Kort 193
Spørgsmål
A Windows client shows 169.254.61.20 and cannot reach its gateway. What should be investigated first?
Svar
DHCP delivery: link/VLAN membership, relay configuration, server reachability, scope capacity, and authorization. The link-local address is evidence that the intended IPv4 lease was not obtained.
Kort 194
Spørgsmål
What does a successful ping prove, and what does it leave unproven?
Svar
It proves an ICMP echo exchange succeeded between the tested endpoints at that moment. It does not prove DNS, the application port, authentication, throughput, or every path works.
Kort 195
Spørgsmål
Users at the edge of a room report slow Wi-Fi and retries. Which RF measurements should be compared?
Svar
Received signal, noise floor, signal-to-noise ratio, retransmissions, data rates, and channel utilization. Low SNR, not distance alone, is the actionable radio symptom.
Kort 196
Spørgsmål
After identifying a problem, how should a troubleshooting theory be formed?
Svar
List plausible causes and rank them by evidence, probability, risk, and ease of testing. A top-down, bottom-up, or divide-and-conquer layer approach can narrow scope; correlation and recent change are clues, not proof.
Kort 197
Spørgsmål
A fiber link is down after installing new optics. Which compatibility details must match?
Svar
Wavelength, fiber type, reach, speed, connector and polish, lane format, and device support. Also compare transmit power and receiver sensitivity against the expected link loss.
Kort 198
Spørgsmål
A user can reach a server by IP address but not by name. Which service is the leading suspect?
Svar
DNS. Check the client's hosts file, resolver settings, exact record, suffix/search behavior, cache, authoritative data, and resolver reachability before changing routes.
Kort 199
Spørgsmål
What does traceroute reveal that ping normally does not?
Svar
It elicits responses from successive hop-limit values to estimate the routed path and where responses stop or change. Missing replies do not always mean forwarding stops because devices may filter or deprioritize probes.
Kort 200
Spørgsmål
Wi-Fi performance collapses when a nearby non-Wi-Fi device operates. What class of fault fits?
Svar
Non-802.11 interference. Use spectrum and WLAN measurements to correlate noise with the event, then remove, relocate, shield, or change band/channel rather than merely adding AP power.
Kort 201
Spørgsmål
What makes a troubleshooting test useful rather than merely disruptive?
Svar
It should isolate one theory, have a predicted result, minimize risk, preserve evidence, and define how to reverse the change. If the theory fails, establish a new theory from the result.
Kort 202
Spørgsmål
A point-to-point link stays down even though the cable or optics match both interfaces. Which TX/RX fault should you check?
Svar
Check for transposed transmit and receive paths: each endpoint's TX must reach the other endpoint's RX. Correct the pair or fiber strands as the interfaces require, then confirm the path with a wiremap or fiber continuity check. Auto-MDI/MDIX can mask some copper pair swaps, but not every wiring or polarity fault.
Kort 203
Spørgsmål
Only one remote subnet is unreachable, while other routed destinations work. What should be compared?
Svar
The destination prefix, next hop, route source and metric, return route, relevant ACLs, and any route filtering. A broad default route can hide a missing specific route in one direction.
Kort 204
Spørgsmål
How do nslookup and dig help isolate a name-resolution problem?
Svar
They query DNS and show records, response status, and the responding server; dig normally exposes more protocol detail. Query both the configured resolver and an authoritative source to locate stale or missing data.
Kort 205
Spørgsmål
Many APs use overlapping channels at high power. Which symptom is likely despite strong signal bars?
Svar
High contention, retries, and poor airtime efficiency. Reduce overlap through channel and power planning; strong received signal does not remove co-channel or adjacent-channel competition.
Kort 206
Spørgsmål
What belongs in a troubleshooting action plan before a risky change?
Svar
Exact steps, owner, timing, dependencies, user and security impact, backups, validation, rollback triggers, communications, and required approval. The plan turns a likely cause into a controlled intervention.
Kort 207
Spørgsmål
What do increasing CRC errors, runts, and giants suggest on an Ethernet interface?
Svar
A Layer 1 or Layer 2 framing problem such as damaged media, interference, duplex trouble, bad hardware, or an MTU/frame-size issue. Compare show-interface counters at both ends and follow the time pattern before replacing equipment.
Kort 208
Spørgsmål
A host reaches local peers but nothing outside its subnet. Which setting should be checked first?
Svar
Its default gateway address and reachability. Then verify subnet mask/prefix, VLAN, ARP or neighbor resolution, gateway interface status, routing, and policy.
Kort 209
Spørgsmål
Which host commands expose current IP addressing on Windows and Linux?
Svar
Windows commonly uses ipconfig; Linux commonly uses ip address from the iproute2 suite, while ifconfig may exist on older systems. Inspect address, prefix, interface state, and default route together.
Kort 210
Spørgsmål
Clients near one AP see good signal but severe adjacent-channel interference. What should change?
Svar
Move the APs to a valid nonoverlapping channel plan, reconsider channel width, and tune transmit power. Confirm with a survey because simply choosing a numerically different channel may still overlap.
Kort 211
Spørgsmål
When should a technician escalate instead of implementing a likely fix alone?
Svar
When authority, expertise, access, vendor support, safety, risk, or outage impact exceeds the technician's scope. Escalate with evidence, tests performed, current impact, and a clear proposed next step.
Kort 212
Spørgsmål
A switch interface is administratively up but protocol down or error-disabled. What should be checked?
Svar
The disable reason, physical link, transceiver or cable, remote port, speed/duplex, VLAN or aggregation policy, and logs. Clear the condition only after correcting the cause.
Kort 213
Spørgsmål
A website loads partially, but large transfers through a tunnel stall. Which path property is a strong suspect?
Svar
An MTU or path-MTU problem. Compare interface and tunnel overhead, test with controlled packet sizes, and correct the narrow segment rather than relying on accidental fragmentation.
Kort 214
Spørgsmål
What do arp and ip neigh reveal during local reachability troubleshooting?
Svar
They show cached IPv4 ARP or IPv6 neighbor mappings and states. A missing, incomplete, or unexpected mapping can point to VLAN, duplicate-address, gateway, or spoofing problems.
Kort 215
Spørgsmål
A phone call drops as a user walks between APs. Which design evidence should be reviewed?
Svar
Coverage overlap, SNR, AP power, channel plan, authentication delay, roaming events, controller logs, and client behavior. The client chooses when to roam, so a single AP's signal view is insufficient.
Kort 216
Spørgsmål
How should a technician verify that a network fix solved the real problem?
Svar
Repeat the original failure condition, confirm normal service and performance, check related systems, monitor for recurrence, and ask affected users. Add preventive controls if the root cause can recur.
Kort 217
Spørgsmål
Several new PoE cameras will not power up, but data links work. What capacity should be checked?
Svar
The switch's total PoE budget and each port's negotiated power class, plus cabling and device standard compatibility. Available port count does not guarantee enough electrical power.
Kort 218
Spørgsmål
Interface utilization stays near capacity during user complaints. Which fault fits, and what evidence is needed?
Svar
Congestion fits. Confirm queue drops, flow sources, traffic class, time pattern, and baseline before adding bandwidth; a loop, backup job, attack, or missing QoS may be the underlying cause.
Kort 219
Spørgsmål
How do netstat or ss and Nmap answer different endpoint questions?
Svar
Netstat or ss shows the local host's listening sockets and connections; Nmap probes targets to discover exposed hosts, ports, or services. Scan only systems you are authorized to assess.
Kort 220
Spørgsmål
A user cannot find the corporate WLAN but sees nearby networks. What should be verified?
Svar
Correct SSID, band and client capability, AP radio state, WLAN-to-AP assignment, broadcast policy, location coverage, and regulatory channel support. Hidden SSIDs can complicate discovery but are not security.
Kort 221
Spørgsmål
What should the final troubleshooting record preserve?
Svar
Symptoms and scope, timeline, evidence, root cause, tests, changes, rollback or validation, affected assets, people notified, final outcome, and preventive follow-up. Avoid undocumented guesses presented as fact.
Kort 222
Spørgsmål
One side of an Ethernet link is full duplex and the other behaves as half duplex. What symptoms can result?
Svar
Low throughput, late collisions on the half-duplex side, FCS errors, and highly uneven performance. Align autonegotiation or matching manual settings at both ends.
Kort 223
Spørgsmål
Voice becomes choppy only when large downloads start. Which policy failure should be examined?
Svar
QoS classification, marking, queuing, shaping, and trust boundaries. Confirm that congestion actually exists on the relevant egress link and that voice retains its markings end to end.
Kort 224
Spørgsmål
What does the route command or ip route output help verify?
Svar
The host or router's known prefixes, next hops, interfaces, defaults, and sometimes source or metric. Compare the chosen route with the destination and expected return path.
Kort 225
Spørgsmål
A client sees the secure SSID but repeatedly fails to join. Which evidence separates authentication from radio trouble?
Svar
Association and authentication logs, certificate time and trust, RADIUS results, EAP method, account state, and whether another known-good client joins at the same spot. Strong signal alone does not prove credentials work.
Kort 226
Spørgsmål
Why should troubleshooting change one variable at a time when practical?
Svar
It preserves causal evidence: if the result changes, the technician can relate it to one intervention. When urgency requires a grouped rollback, document the bundle and test components later.
Kort 227
Spørgsmål
A replacement transceiver fits the port but the link stays down. Why is form factor alone insufficient?
Svar
The module must match speed, wavelength, reach, fiber or copper medium, lane/breakout format, and device support at both ends. Check diagnostics and vendor compatibility rather than only connector shape.
Kort 228
Spørgsmål
Which measurements distinguish delay, variable delay, and missing traffic?
Svar
Latency measures delay, jitter measures variation, and packet-loss rate measures missing packets. A controlled speed test estimates throughput; collect results over time because averages can hide brief service-breaking spikes.
Kort 229
Spørgsmål
When should tcpdump or Wireshark be used in a troubleshooting sequence?
Svar
When packet-level evidence can distinguish protocol behavior, retransmission, resets, negotiation, or policy. Capture at the right point with a narrow filter, protect sensitive payloads, and compare timestamps.
Kort 230
Spørgsmål
Two Wi-Fi clients hear an AP but not each other and collide when transmitting. What RF issue fits?
Svar
The hidden-node problem. RTS/CTS behavior, AP placement, cell size, band/channel design, or relocating clients can reduce collisions; adding transmit power indiscriminately may worsen contention.
Kort 231
Spørgsmål
A long copper run links at a lower speed and shows errors. Which distance-related faults should be considered?
Svar
Excessive insertion loss, crosstalk, poor termination, damaged pairs, electromagnetic interference, or a run beyond the standard's channel length. Certify the permanent link rather than trusting continuity alone.
Kort 232
Spørgsmål
Users in one VLAN cannot reach a service, while users in another VLAN can. What should be compared?
Svar
VLAN membership, trunk allowance, SVI or gateway state, subnet and DHCP options, inter-VLAN route, ACL or firewall policy, and the service's return path.
Kort 233
Spørgsmål
When does a toner probe help more than a cable certifier?
Svar
When locating an unlabeled copper cable or its far-end port. A certifier measures whether a link meets performance standards; a toner primarily helps trace identity and path.
Kort 234
Spørgsmål
A lecture hall WLAN works empty but fails when full. Which design limit is most likely?
Svar
Capacity or airtime, not simple coverage. Measure concurrent clients, channel utilization, data rates, retries, application demand, uplink capacity, and AP distribution under real load.
Kort 235
Spørgsmål
A fiber link's receive power gradually drops over weeks. Which physical causes fit?
Svar
Dirty or damaged connectors, a loosening bend, stressed cable, aging optics, or a changing patch path. Inspect and clean correctly, then compare optical power with the link budget and earlier baseline.
Kort 236
Spørgsmål
A service works from most networks but not one source subnet. Which policy fault is likely?
Svar
An ACL or firewall rule with the wrong source, destination, port, direction, order, or state assumption. Read hit counters and logs, and verify the return path before broadening access.
Kort 237
Spørgsmål
What does an optical power meter measure during fiber troubleshooting?
Svar
An optical meter measures received power, usually in dBm; a visual fault locator injects visible light to expose nearby breaks or bends. Compare measured power with receiver limits and the link budget.
Kort 238
Spørgsmål
A dual-band client clings to distant 2.4 GHz despite a nearby 5 GHz AP. What should be tuned?
Svar
Coverage, AP transmit power, band steering, minimum data rates, roaming thresholds if exposed, and client drivers. Preserve adequate 2.4 GHz service for devices that genuinely require it.
Kort 239
Spørgsmål
A cable passes simple continuity but performs poorly at gigabit speed. Which wiring fault may remain?
Svar
A split pair or excessive crosstalk can preserve pin-to-pin continuity while violating pair geometry. Use a qualification or certification tester that measures performance, not only wiremap continuity.
Kort 240
Spørgsmål
Certificates fail on many devices immediately after a time-source outage. What is the likely connection?
Svar
Incorrect clocks can make valid certificates appear not yet valid or expired and can break time-sensitive authentication. Restore a trusted time hierarchy, then verify timezone display separately from UTC time.
Kort 241
Spørgsmål
What should a protocol analyzer's capture location be chosen to prove?
Svar
Whether packets enter, cross, or leave a suspected boundary and how they change. Captures on both sides can distinguish endpoint behavior, loss, translation, filtering, and asymmetric routing.
Kort 242
Spørgsmål
A point-to-point wireless bridge becomes unstable after an antenna is moved. What should be rechecked?
Svar
Alignment, polarization, mounting, cable and connector loss, line-of-sight, Fresnel clearance, received signal, noise, channel, and local transmit-power limits.
Kort 243
Spørgsmål
A switch network suddenly floods broadcasts and MAC addresses flap between ports. What physical or Layer 2 fault fits?
Svar
A switching loop, possibly from an unintended cable or failed STP protection. Contain the loop, preserve evidence, trace the ports, then correct topology and loop-prevention controls.
Kort 244
Spørgsmål
Two hosts intermittently lose connectivity and report the same IPv4 address. What should be checked?
Svar
A duplicate address from conflicting static assignments, a stale reservation, or an unauthorized DHCP server. Trace both MAC addresses, correct the source, and refresh neighbor and lease state.
Kort 245
Spørgsmål
How can LLDP or a vendor discovery protocol speed physical topology troubleshooting?
Svar
It reports directly connected device identity, port, capabilities, and sometimes VLAN or power details. Treat discovery data as evidence to verify, because it may be disabled, stale, or spoofed.
Kort 246
Spørgsmål
A 5 GHz AP changes channel or pauses after detecting radar. Is that necessarily a fault?
Svar
No. Dynamic Frequency Selection requires affected channels to detect radar and vacate when necessary. Check DFS events, regulatory domain, channel plan, and client support before blaming hardware.
Kort 247
Spørgsmål
During an STP loop investigation, which port roles and states should you expect?
Svar
Each non-root switch selects one root port, each segment selects one designated port, and redundant paths can use alternate or backup ports. Classic 802.1D states are blocking, listening, learning, forwarding, and disabled; RSTP uses discarding, learning, and forwarding. Verify the intended root bridge because its placement determines the roles.
Kort 248
Spørgsmål
Internal clients reach the internet, but a new inbound service is unreachable through NAT. What should be verified?
Svar
The static or port-forward mapping, public address, listening service, firewall policy, return route, overlapping ports, and upstream filtering. Outbound PAT working does not prove unsolicited inbound translation exists.
Kort 249
Spørgsmål
Traceroute repeats a small set of routers until the hop limit expires. What fault does that pattern suggest?
Svar
A routing loop. Compare the relevant prefixes, next hops, redistribution, defaults, and recent changes on the repeating routers, then correct the inconsistent route information.
Kort 250
Spørgsmål
A guest joins Wi-Fi and receives an address but cannot browse until opening a plain HTTP site. What should be tested?
Svar
Captive-portal detection and redirection, DNS, portal reachability, certificate behavior, allowed preauthentication traffic, client isolation, and completion state. The radio and DHCP path already appear functional.

Abstract network core linked to cloud, wireless, switching, storage, and diagnostic nodes in navy, cyan, and coral.

250 kort