Common Network Port Numbers Flashcards: Protocols, TCP/UDP & Uses
Study 88 cards on common network ports, TCP/UDP transports, service uses, port ranges, and practical protocol distinctions.
Om den här kortleken
Build a practical map of common network service ports with 88 independently authored cards. Twelve foundation and distinction cards cover port roles, IANA ranges, independent TCP and UDP namespaces, assignment limits, conventional versus configured ports, client source ports, DNS transport behavior, DHCP endpoints, FTP channels, and common implicit-TLS pairs.
The remaining 76 cards practice 38 mappings in both useful directions: service → conventional or registered port, transport, and concise use; and port/transport → service and concise use. Coverage includes FTP control and active-mode data, SSH/SFTP, Telnet, SMTP relay, DNS, DHCPv4 server and client endpoints, TFTP, HTTP, Kerberos, POP3, NTP, the three NetBIOS services, IMAP, SNMP queries and notifications, BGP, LDAP, HTTPS including HTTP/3, direct-hosted SMB, IKE, syslog, SMTP submission, LDAPS, IMAPS, POP3S, Microsoft SQL Server, L2TP, PPTP, RADIUS authentication, MySQL, RDP, IPsec NAT Traversal, SIP, and PostgreSQL.
This is a focused recall deck, not a copy of the full IANA registry. It excludes exhaustive assignments, port-scanning or attack instructions, firewall policy, every vendor-specific alternate, dynamic service-discovery inventories, and the claim that a port number proves which application produced observed traffic. Registered, default, conventional, and common-use wording stays explicit because services can be reconfigured or negotiated elsewhere.
The sequence establishes the port model first, then mixes web, email, infrastructure, remote-access, file-transfer, network-management, directory, VPN, voice, Windows, and database families. Opposite directions for the same mapping stay at least 38 intervening cards apart. Near-duplicate DNS, DHCP, FTP, SNMP, NetBIOS, and IPsec cues keep at least three unrelated cards between them, and the TLS-pair distinction stays at least three unrelated cards from its closest overlapping mapping. The review scheduler handles continued spacing after installation.
Open Study Contributor independently authored the prompts, answers, mapping choices, organization, metadata, and cover from common networking knowledge checked against the current IANA Service Name and Transport Protocol Port Number Registry, relevant RFCs, and official vendor documentation. Organization and product names identify protocols, services, or sources only; no affiliation or endorsement is claimed. No competitor card text, certification questions, answer keys, course text, or source prose was copied.
The CC0 label applies to the original prompts, answers, organization, metadata, and generated cover to the extent applicable rights exist. It does not claim ownership of protocol facts, standards, organization names, product names, or third-party source material.
Kort i den här kortleken
Kort 1
Fråga
What does a transport-layer port number identify?
Svar
An application endpoint within a host for one transport protocol. The IP addresses, transport protocol, and source and destination ports together identify a communication flow.
Kort 2
Fråga
Are TCP port 53 and UDP port 53 the same port?
Svar
No. TCP and UDP have independent 16-bit port namespaces, so 53/TCP and 53/UDP are separate transport endpoints.
Kort 3
Fråga
What is the IANA System Port range?
Svar
0–1023. These are also called Well-Known Ports and are assigned by IANA under the stricter System Port procedures.
Kort 4
Fråga
What is the IANA User Port range?
Svar
1024–49151. These are also called Registered Ports and may be assigned by IANA to services.
Kort 5
Fråga
What is the IANA Dynamic or Private Port range?
Svar
49152–65535. IANA does not assign ports in this range; systems commonly use it for temporary or private endpoints.
Kort 6
Fråga
Does an IANA port assignment prove what observed traffic is—or that it is safe?
Svar
No. A registration is a naming convention, not traffic identification, authorization, or a security verdict. Verify the actual protocol and context.
Kort 7
Fråga
Must a service use its registered or conventional port?
Svar
No. Administrators and applications can choose another port, negotiate one dynamically, or discover it through mechanisms such as DNS SRV records.
Kort 8
Fråga
What port roles are typical in a client-server connection?
Svar
The server usually listens on a known destination port, while the client uses a temporary source port. Either side can be configured differently.
Kort 9
Fråga
SSH and SFTP — common server port and transport?
Svar
TCP 22. SSH provides encrypted remote access, and SFTP normally runs as a subsystem inside the same SSH connection.
Kort 10
Fråga
53/UDP or 53/TCP — which service?
Svar
DNS. Routine queries often use UDP, while full DNS implementations also support TCP; zone transfers use TCP.
Kort 11
Fråga
SMTP relay between mail servers — common port and transport?
Svar
TCP 25. SMTP uses it for server-to-server mail transfer; user mail submission normally uses port 587 or implicit TLS on 465.
Kort 12
Fråga
HTTP without TLS — conventional port and transport?
Svar
TCP 80 for conventional HTTP/1.1 and HTTP/2 connections. The service can be configured on another port.
Kort 13
Fråga
67/UDP — which DHCPv4 endpoint?
Svar
The DHCPv4 server endpoint. Clients send server-directed DHCP messages to UDP port 67.
Kort 14
Fråga
21/TCP — which service and channel?
Svar
FTP control. It carries commands and replies; file data uses a separate connection.
Kort 15
Fråga
SNMP requests and responses — common agent port and transport?
Svar
UDP 161. Managers commonly send queries to an SNMP agent there; other SNMP transports exist.
Kort 16
Fråga
1433/TCP — which database service?
Svar
Microsoft SQL Server's default instance. TCP 1433 is the default Database Engine port, but named or custom instances may use another port.
Kort 17
Fråga
23/TCP — which remote-access protocol?
Svar
Telnet. It provides a plaintext remote terminal session and does not protect credentials or traffic with encryption.
Kort 18
Fråga
NTP — usual port and transport?
Svar
UDP 123. NTP normally uses UDP for time synchronization; IANA also has a TCP 123 registration, but that is not the usual NTP transport.
Kort 19
Fråga
Why must a general-purpose DNS implementation support both UDP and TCP?
Svar
UDP handles most routine queries efficiently, while TCP handles cases such as zone transfers and responses that do not fit the chosen UDP path. Both use port 53.
Kort 20
Fråga
POP3 — conventional port and transport?
Svar
TCP 110. POP3 retrieves mail; it can upgrade with STLS, while implicit TLS uses TCP 995.
Kort 21
Fråga
443/TCP or 443/UDP — which web service?
Svar
HTTPS. HTTP/1.1 and HTTP/2 normally use TLS over TCP 443; HTTP/3 uses QUIC over UDP 443.
Kort 22
Fråga
DHCPv4 client endpoint — port and transport?
Svar
UDP 68. Servers send client-directed DHCPv4 messages to port 68.
Kort 23
Fråga
69/UDP — which file-transfer protocol?
Svar
TFTP. A client sends the initial read or write request to UDP 69; the transfer then continues with a server-selected UDP transfer identifier.
Kort 24
Fråga
162/UDP — which network-management traffic?
Svar
SNMP notifications, traditionally called traps. Notification receivers commonly listen on UDP 162.
Kort 25
Fråga
MySQL classic protocol — default port and transport?
Svar
TCP 3306. It is the default for classic MySQL client-server connections and can be reconfigured.
Kort 26
Fråga
How do FTP control, active-mode data, and passive-mode data ports differ?
Svar
Control uses TCP 21. The server side of the default active-mode data connection uses TCP 20, while passive mode negotiates another server port.
Kort 27
Fråga
3389/TCP or 3389/UDP — which remote-desktop service?
Svar
Microsoft Remote Desktop Protocol (RDP). TCP and UDP 3389 are the standard defaults, and the listening port can be changed.
Kort 28
Fråga
Syslog's conventional UDP transport — port?
Svar
UDP 514. Classic syslog over UDP has no delivery guarantee; TCP 514 is registered to the shell service, not syslog.
Kort 29
Fråga
How do DHCPv4 server and client ports pair up?
Svar
UDP 67 is the server port, and UDP 68 is the client port. Client-to-server messages target 67; server-to-client messages target 68.
Kort 30
Fråga
IMAP — conventional port and transport?
Svar
TCP 143. IMAP accesses and manages mail on a server; implicit TLS uses TCP 993.
Kort 31
Fråga
445/TCP — which file-sharing service?
Svar
Direct-hosted SMB. Modern SMB servers commonly listen on TCP 445 without the older NetBIOS session layer.
Kort 32
Fråga
88/UDP or 88/TCP — which authentication protocol?
Svar
Kerberos. Clients and Key Distribution Centers support both transports; TCP also handles requests or replies too large for UDP.
Kort 33
Fråga
FTP's default active-mode data connection — server-side port and transport?
Svar
TCP 20. This is the server's default source port for active-mode data; passive FTP negotiates another server port.
Kort 34
Fråga
BGP — standard operational port and transport?
Svar
TCP 179. RFC 4271 defines BGP peer sessions over TCP; IANA separately retains a UDP 179 registry entry.
Kort 35
Fråga
5432/TCP — which database service?
Svar
PostgreSQL. TCP 5432 is the customary default server port, but an installation can choose another port.
Kort 36
Fråga
IKE for IPsec — initial port and transport?
Svar
UDP 500. IKE normally begins there; NAT traversal commonly moves subsequent IKE and encapsulated ESP traffic to UDP 4500.
Kort 37
Fråga
NetBIOS Name Service — common port and transport?
Svar
UDP 137. It supports NetBIOS name registration and lookup; direct-hosted modern SMB does not require it.
Kort 38
Fråga
587/TCP — which email role?
Svar
SMTP message submission. Mail clients normally submit outgoing mail to a submission server there, often with STARTTLS; server relay remains on TCP 25.
Kort 39
Fråga
389/TCP — which directory protocol?
Svar
LDAP. Ordinary connection-oriented LDAP commonly uses TCP 389; IANA also registers UDP 389 for connectionless LDAP.
Kort 40
Fråga
L2TP — common port and transport?
Svar
UDP 1701. L2TP carries tunnel control and data but does not provide encryption by itself; deployments often pair it with IPsec.
Kort 41
Fråga
138/UDP — which NetBIOS service?
Svar
NetBIOS Datagram Service. It carries connectionless NetBIOS datagrams, historically used in NetBIOS over TCP/IP environments.
Kort 42
Fråga
IMAPS — default port and transport?
Svar
TCP 993. It starts IMAP with an immediate TLS handshake for encrypted mail access.
Kort 43
Fråga
636/TCP — which directory-service convention?
Svar
LDAPS, the commonly used implicit-TLS port for LDAP. LDAP can also negotiate TLS on TCP 389.
Kort 44
Fråga
1723/TCP — which VPN control protocol?
Svar
PPTP control. PPTP uses TCP 1723 for control, while tunneled PPP data travels in GRE—not on TCP or UDP port 47.
Kort 45
Fråga
NetBIOS Session Service — common port and transport?
Svar
TCP 139. It provides connection-oriented NetBIOS sessions and historically carried SMB before direct-hosted SMB on TCP 445.
Kort 46
Fråga
995/TCP — which mail-access service?
Svar
POP3S. It starts POP3 with an immediate TLS handshake for encrypted mail retrieval.
Kort 47
Fråga
RADIUS authentication and authorization — standard port and transport?
Svar
UDP 1812. RADIUS accounting normally uses the separate UDP port 1813.
Kort 48
Fråga
IPsec NAT Traversal — port and transport?
Svar
UDP 4500. It carries IKE and UDP-encapsulated ESP when NAT traversal is in use.
Kort 49
Fråga
5060/UDP or 5060/TCP — which signaling protocol?
Svar
SIP. It commonly uses UDP or TCP 5060 for session signaling; SIP over TLS conventionally uses TCP 5061.
Kort 50
Fråga
Which common dedicated ports distinguish plaintext or STARTTLS-capable services from implicit-TLS variants?
Svar
HTTP 80 ↔ HTTPS 443; IMAP 143 ↔ IMAPS 993; POP3 110 ↔ POP3S 995; LDAP 389 ↔ LDAPS 636. A port alone does not prove that TLS is configured correctly.
Kort 51
Fråga
22/TCP — which secure remote-access service?
Svar
SSH. It supports encrypted remote login, command execution, tunneling, and file-transfer tools such as SFTP.
Kort 52
Fråga
DNS — registered port and required general-purpose transports?
Svar
Port 53 over UDP and TCP. Most ordinary queries start with UDP, while TCP is required for full implementations and used for zone transfers and other larger exchanges.
Kort 53
Fråga
25/TCP — which email function?
Svar
SMTP mail relay and delivery between servers. End-user clients normally submit new mail on TCP 587 or TCP 465 instead.
Kort 54
Fråga
80/TCP — which conventional web service?
Svar
HTTP without TLS. It is the conventional port for HTTP/1.1 and HTTP/2, although servers can listen elsewhere.
Kort 55
Fråga
DHCPv4 server endpoint — port and transport?
Svar
UDP 67. DHCPv4 clients direct server-bound messages to that port.
Kort 56
Fråga
FTP control — server port and transport?
Svar
TCP 21. Commands and replies use the persistent control connection; data travels on a separate connection.
Kort 57
Fråga
161/UDP — which network-management traffic?
Svar
SNMP requests and responses. Managed agents commonly listen on UDP 161 for manager queries.
Kort 58
Fråga
Microsoft SQL Server default instance — default port and transport?
Svar
TCP 1433. Named instances may use dynamic or custom ports, with SQL Server Browser commonly using UDP 1434 for discovery.
Kort 59
Fråga
Telnet — conventional port and transport?
Svar
TCP 23. Telnet carries terminal traffic in plaintext, so SSH is the usual secure replacement.
Kort 60
Fråga
123/UDP — which time service?
Svar
NTP. Network Time Protocol commonly synchronizes clocks over UDP 123.
Kort 61
Fråga
110/TCP — which mail-access protocol?
Svar
POP3. It downloads or retrieves mail from a server; implicit TLS uses TCP 995.
Kort 62
Fråga
HTTPS — common port and transports?
Svar
Port 443: TCP for HTTP/1.1 and HTTP/2 over TLS, and UDP for HTTP/3 over QUIC.
Kort 63
Fråga
68/UDP — which DHCPv4 endpoint?
Svar
The DHCPv4 client endpoint. Servers direct client-bound DHCP messages to UDP 68.
Kort 64
Fråga
TFTP — initial request port and transport?
Svar
UDP 69. Only the initial request targets 69; the server chooses another UDP transfer identifier for the data exchange.
Kort 65
Fråga
SNMP traps and other notifications — common receiver port and transport?
Svar
UDP 162. SNMP notification receivers commonly listen there.
Kort 66
Fråga
3306/TCP — which database protocol?
Svar
The classic MySQL protocol. TCP 3306 is its default client-server port and is configurable.
Kort 67
Fråga
RDP — standard port and transports?
Svar
TCP and UDP 3389. Microsoft Remote Desktop uses them by default, though administrators can change the listening port.
Kort 68
Fråga
514/UDP — which logging protocol?
Svar
Syslog over UDP. It is a conventional lightweight transport without delivery guarantees; secure syslog commonly uses another transport and port.
Kort 69
Fråga
143/TCP — which mail-access protocol?
Svar
IMAP. It manages mail on the server; implicit TLS uses TCP 993.
Kort 70
Fråga
Direct-hosted SMB — common server port and transport?
Svar
TCP 445. It carries SMB directly over TCP without the legacy NetBIOS Session Service on TCP 139.
Kort 71
Fråga
Kerberos KDC traffic — port and transports?
Svar
UDP and TCP 88. Conforming clients and Key Distribution Centers support both, with TCP available for larger exchanges.
Kort 72
Fråga
20/TCP — which FTP role?
Svar
The server side of FTP's default active-mode data connection. Passive mode negotiates a different server port.
Kort 73
Fråga
179/TCP — which routing protocol?
Svar
BGP. Border Gateway Protocol peers use a TCP session to exchange routing information.
Kort 74
Fråga
PostgreSQL — customary default port and transport?
Svar
TCP 5432. PostgreSQL servers normally use it unless configured or compiled with another default.
Kort 75
Fråga
500/UDP — which IPsec setup protocol?
Svar
IKE, the Internet Key Exchange protocol. It negotiates IPsec security associations and commonly moves to UDP 4500 when NAT traversal is used.
Kort 76
Fråga
137/UDP — which NetBIOS service?
Svar
NetBIOS Name Service. It handles name registration and lookup in legacy NetBIOS over TCP/IP environments.
Kort 77
Fråga
SMTP message submission — normal port and transport?
Svar
TCP 587. It separates authenticated client submission from server-to-server SMTP relay on TCP 25; STARTTLS is commonly used.
Kort 78
Fråga
LDAP — conventional connection-oriented port and transport?
Svar
TCP 389. Connectionless LDAP can use UDP 389, and implicit-TLS LDAP commonly uses TCP 636.
Kort 79
Fråga
1701/UDP — which tunneling protocol?
Svar
L2TP. It tunnels Layer 2 traffic but needs a separate security layer such as IPsec when confidentiality is required.
Kort 80
Fråga
NetBIOS Datagram Service — common port and transport?
Svar
UDP 138. It provides connectionless NetBIOS datagram delivery.
Kort 81
Fråga
993/TCP — which mail-access service?
Svar
IMAPS. It begins IMAP with implicit TLS for encrypted access to mail stored on a server.
Kort 82
Fråga
LDAPS — commonly used implicit-TLS port and transport?
Svar
TCP 636. LDAP can instead use TCP 389 and negotiate TLS with StartTLS.
Kort 83
Fråga
PPTP control — port and transport?
Svar
TCP 1723. The control channel uses that port; PPP payloads travel through GRE, which is IP protocol 47 rather than port 47.
Kort 84
Fråga
139/TCP — which NetBIOS service?
Svar
NetBIOS Session Service. It historically carried SMB sessions; direct-hosted SMB commonly uses TCP 445 instead.
Kort 85
Fråga
POP3S — default port and transport?
Svar
TCP 995. It uses implicit TLS for encrypted POP3 mail retrieval.
Kort 86
Fråga
1812/UDP — which AAA service?
Svar
RADIUS authentication and authorization. RADIUS accounting normally uses UDP 1813.
Kort 87
Fråga
4500/UDP — which IPsec function?
Svar
IPsec NAT Traversal. It carries IKE and UDP-encapsulated ESP across network address translation.
Kort 88
Fråga
SIP signaling without implicit TLS — common port and transports?
Svar
UDP or TCP 5060. SIP over TLS conventionally uses TCP 5061, and media streams use separately negotiated ports.
88 kort
Common Network Port Numbers Flashcards: Protocols, TCP/UDP & Uses
Nibomo öppnas så att du kan börja plugga.