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.
Tentang dek ini
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.
Kad dalam dek ini
Kad 1
Soalan
What does a transport-layer port number identify?
Jawapan
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.
Kad 2
Soalan
Are TCP port 53 and UDP port 53 the same port?
Jawapan
No. TCP and UDP have independent 16-bit port namespaces, so 53/TCP and 53/UDP are separate transport endpoints.
Kad 3
Soalan
What is the IANA System Port range?
Jawapan
0–1023. These are also called Well-Known Ports and are assigned by IANA under the stricter System Port procedures.
Kad 4
Soalan
What is the IANA User Port range?
Jawapan
1024–49151. These are also called Registered Ports and may be assigned by IANA to services.
Kad 5
Soalan
What is the IANA Dynamic or Private Port range?
Jawapan
49152–65535. IANA does not assign ports in this range; systems commonly use it for temporary or private endpoints.
Kad 6
Soalan
Does an IANA port assignment prove what observed traffic is—or that it is safe?
Jawapan
No. A registration is a naming convention, not traffic identification, authorization, or a security verdict. Verify the actual protocol and context.
Kad 7
Soalan
Must a service use its registered or conventional port?
Jawapan
No. Administrators and applications can choose another port, negotiate one dynamically, or discover it through mechanisms such as DNS SRV records.
Kad 8
Soalan
What port roles are typical in a client-server connection?
Jawapan
The server usually listens on a known destination port, while the client uses a temporary source port. Either side can be configured differently.
Kad 9
Soalan
SSH and SFTP — common server port and transport?
Jawapan
TCP 22. SSH provides encrypted remote access, and SFTP normally runs as a subsystem inside the same SSH connection.
Kad 10
Soalan
53/UDP or 53/TCP — which service?
Jawapan
DNS. Routine queries often use UDP, while full DNS implementations also support TCP; zone transfers use TCP.
Kad 11
Soalan
SMTP relay between mail servers — common port and transport?
Jawapan
TCP 25. SMTP uses it for server-to-server mail transfer; user mail submission normally uses port 587 or implicit TLS on 465.
Kad 12
Soalan
HTTP without TLS — conventional port and transport?
Jawapan
TCP 80 for conventional HTTP/1.1 and HTTP/2 connections. The service can be configured on another port.
Kad 13
Soalan
67/UDP — which DHCPv4 endpoint?
Jawapan
The DHCPv4 server endpoint. Clients send server-directed DHCP messages to UDP port 67.
Kad 14
Soalan
21/TCP — which service and channel?
Jawapan
FTP control. It carries commands and replies; file data uses a separate connection.
Kad 15
Soalan
SNMP requests and responses — common agent port and transport?
Jawapan
UDP 161. Managers commonly send queries to an SNMP agent there; other SNMP transports exist.
Kad 16
Soalan
1433/TCP — which database service?
Jawapan
Microsoft SQL Server's default instance. TCP 1433 is the default Database Engine port, but named or custom instances may use another port.
Kad 17
Soalan
23/TCP — which remote-access protocol?
Jawapan
Telnet. It provides a plaintext remote terminal session and does not protect credentials or traffic with encryption.
Kad 18
Soalan
NTP — usual port and transport?
Jawapan
UDP 123. NTP normally uses UDP for time synchronization; IANA also has a TCP 123 registration, but that is not the usual NTP transport.
Kad 19
Soalan
Why must a general-purpose DNS implementation support both UDP and TCP?
Jawapan
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.
Kad 20
Soalan
POP3 — conventional port and transport?
Jawapan
TCP 110. POP3 retrieves mail; it can upgrade with STLS, while implicit TLS uses TCP 995.
Kad 21
Soalan
443/TCP or 443/UDP — which web service?
Jawapan
HTTPS. HTTP/1.1 and HTTP/2 normally use TLS over TCP 443; HTTP/3 uses QUIC over UDP 443.
Kad 22
Soalan
DHCPv4 client endpoint — port and transport?
Jawapan
UDP 68. Servers send client-directed DHCPv4 messages to port 68.
Kad 23
Soalan
69/UDP — which file-transfer protocol?
Jawapan
TFTP. A client sends the initial read or write request to UDP 69; the transfer then continues with a server-selected UDP transfer identifier.
Kad 24
Soalan
162/UDP — which network-management traffic?
Jawapan
SNMP notifications, traditionally called traps. Notification receivers commonly listen on UDP 162.
Kad 25
Soalan
MySQL classic protocol — default port and transport?
Jawapan
TCP 3306. It is the default for classic MySQL client-server connections and can be reconfigured.
Kad 26
Soalan
How do FTP control, active-mode data, and passive-mode data ports differ?
Jawapan
Control uses TCP 21. The server side of the default active-mode data connection uses TCP 20, while passive mode negotiates another server port.
Kad 27
Soalan
3389/TCP or 3389/UDP — which remote-desktop service?
Jawapan
Microsoft Remote Desktop Protocol (RDP). TCP and UDP 3389 are the standard defaults, and the listening port can be changed.
Kad 28
Soalan
Syslog's conventional UDP transport — port?
Jawapan
UDP 514. Classic syslog over UDP has no delivery guarantee; TCP 514 is registered to the shell service, not syslog.
Kad 29
Soalan
How do DHCPv4 server and client ports pair up?
Jawapan
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.
Kad 30
Soalan
IMAP — conventional port and transport?
Jawapan
TCP 143. IMAP accesses and manages mail on a server; implicit TLS uses TCP 993.
Kad 31
Soalan
445/TCP — which file-sharing service?
Jawapan
Direct-hosted SMB. Modern SMB servers commonly listen on TCP 445 without the older NetBIOS session layer.
Kad 32
Soalan
88/UDP or 88/TCP — which authentication protocol?
Jawapan
Kerberos. Clients and Key Distribution Centers support both transports; TCP also handles requests or replies too large for UDP.
Kad 33
Soalan
FTP's default active-mode data connection — server-side port and transport?
Jawapan
TCP 20. This is the server's default source port for active-mode data; passive FTP negotiates another server port.
Kad 34
Soalan
BGP — standard operational port and transport?
Jawapan
TCP 179. RFC 4271 defines BGP peer sessions over TCP; IANA separately retains a UDP 179 registry entry.
Kad 35
Soalan
5432/TCP — which database service?
Jawapan
PostgreSQL. TCP 5432 is the customary default server port, but an installation can choose another port.
Kad 36
Soalan
IKE for IPsec — initial port and transport?
Jawapan
UDP 500. IKE normally begins there; NAT traversal commonly moves subsequent IKE and encapsulated ESP traffic to UDP 4500.
Kad 37
Soalan
NetBIOS Name Service — common port and transport?
Jawapan
UDP 137. It supports NetBIOS name registration and lookup; direct-hosted modern SMB does not require it.
Kad 38
Soalan
587/TCP — which email role?
Jawapan
SMTP message submission. Mail clients normally submit outgoing mail to a submission server there, often with STARTTLS; server relay remains on TCP 25.
Kad 39
Soalan
389/TCP — which directory protocol?
Jawapan
LDAP. Ordinary connection-oriented LDAP commonly uses TCP 389; IANA also registers UDP 389 for connectionless LDAP.
Kad 40
Soalan
L2TP — common port and transport?
Jawapan
UDP 1701. L2TP carries tunnel control and data but does not provide encryption by itself; deployments often pair it with IPsec.
Kad 41
Soalan
138/UDP — which NetBIOS service?
Jawapan
NetBIOS Datagram Service. It carries connectionless NetBIOS datagrams, historically used in NetBIOS over TCP/IP environments.
Kad 42
Soalan
IMAPS — default port and transport?
Jawapan
TCP 993. It starts IMAP with an immediate TLS handshake for encrypted mail access.
Kad 43
Soalan
636/TCP — which directory-service convention?
Jawapan
LDAPS, the commonly used implicit-TLS port for LDAP. LDAP can also negotiate TLS on TCP 389.
Kad 44
Soalan
1723/TCP — which VPN control protocol?
Jawapan
PPTP control. PPTP uses TCP 1723 for control, while tunneled PPP data travels in GRE—not on TCP or UDP port 47.
Kad 45
Soalan
NetBIOS Session Service — common port and transport?
Jawapan
TCP 139. It provides connection-oriented NetBIOS sessions and historically carried SMB before direct-hosted SMB on TCP 445.
Kad 46
Soalan
995/TCP — which mail-access service?
Jawapan
POP3S. It starts POP3 with an immediate TLS handshake for encrypted mail retrieval.
Kad 47
Soalan
RADIUS authentication and authorization — standard port and transport?
Jawapan
UDP 1812. RADIUS accounting normally uses the separate UDP port 1813.
Kad 48
Soalan
IPsec NAT Traversal — port and transport?
Jawapan
UDP 4500. It carries IKE and UDP-encapsulated ESP when NAT traversal is in use.
Kad 49
Soalan
5060/UDP or 5060/TCP — which signaling protocol?
Jawapan
SIP. It commonly uses UDP or TCP 5060 for session signaling; SIP over TLS conventionally uses TCP 5061.
Kad 50
Soalan
Which common dedicated ports distinguish plaintext or STARTTLS-capable services from implicit-TLS variants?
Jawapan
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.
Kad 51
Soalan
22/TCP — which secure remote-access service?
Jawapan
SSH. It supports encrypted remote login, command execution, tunneling, and file-transfer tools such as SFTP.
Kad 52
Soalan
DNS — registered port and required general-purpose transports?
Jawapan
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.
Kad 53
Soalan
25/TCP — which email function?
Jawapan
SMTP mail relay and delivery between servers. End-user clients normally submit new mail on TCP 587 or TCP 465 instead.
Kad 54
Soalan
80/TCP — which conventional web service?
Jawapan
HTTP without TLS. It is the conventional port for HTTP/1.1 and HTTP/2, although servers can listen elsewhere.
Kad 55
Soalan
DHCPv4 server endpoint — port and transport?
Jawapan
UDP 67. DHCPv4 clients direct server-bound messages to that port.
Kad 56
Soalan
FTP control — server port and transport?
Jawapan
TCP 21. Commands and replies use the persistent control connection; data travels on a separate connection.
Kad 57
Soalan
161/UDP — which network-management traffic?
Jawapan
SNMP requests and responses. Managed agents commonly listen on UDP 161 for manager queries.
Kad 58
Soalan
Microsoft SQL Server default instance — default port and transport?
Jawapan
TCP 1433. Named instances may use dynamic or custom ports, with SQL Server Browser commonly using UDP 1434 for discovery.
Kad 59
Soalan
Telnet — conventional port and transport?
Jawapan
TCP 23. Telnet carries terminal traffic in plaintext, so SSH is the usual secure replacement.
Kad 60
Soalan
123/UDP — which time service?
Jawapan
NTP. Network Time Protocol commonly synchronizes clocks over UDP 123.
Kad 61
Soalan
110/TCP — which mail-access protocol?
Jawapan
POP3. It downloads or retrieves mail from a server; implicit TLS uses TCP 995.
Kad 62
Soalan
HTTPS — common port and transports?
Jawapan
Port 443: TCP for HTTP/1.1 and HTTP/2 over TLS, and UDP for HTTP/3 over QUIC.
Kad 63
Soalan
68/UDP — which DHCPv4 endpoint?
Jawapan
The DHCPv4 client endpoint. Servers direct client-bound DHCP messages to UDP 68.
Kad 64
Soalan
TFTP — initial request port and transport?
Jawapan
UDP 69. Only the initial request targets 69; the server chooses another UDP transfer identifier for the data exchange.
Kad 65
Soalan
SNMP traps and other notifications — common receiver port and transport?
Jawapan
UDP 162. SNMP notification receivers commonly listen there.
Kad 66
Soalan
3306/TCP — which database protocol?
Jawapan
The classic MySQL protocol. TCP 3306 is its default client-server port and is configurable.
Kad 67
Soalan
RDP — standard port and transports?
Jawapan
TCP and UDP 3389. Microsoft Remote Desktop uses them by default, though administrators can change the listening port.
Kad 68
Soalan
514/UDP — which logging protocol?
Jawapan
Syslog over UDP. It is a conventional lightweight transport without delivery guarantees; secure syslog commonly uses another transport and port.
Kad 69
Soalan
143/TCP — which mail-access protocol?
Jawapan
IMAP. It manages mail on the server; implicit TLS uses TCP 993.
Kad 70
Soalan
Direct-hosted SMB — common server port and transport?
Jawapan
TCP 445. It carries SMB directly over TCP without the legacy NetBIOS Session Service on TCP 139.
Kad 71
Soalan
Kerberos KDC traffic — port and transports?
Jawapan
UDP and TCP 88. Conforming clients and Key Distribution Centers support both, with TCP available for larger exchanges.
Kad 72
Soalan
20/TCP — which FTP role?
Jawapan
The server side of FTP's default active-mode data connection. Passive mode negotiates a different server port.
Kad 73
Soalan
179/TCP — which routing protocol?
Jawapan
BGP. Border Gateway Protocol peers use a TCP session to exchange routing information.
Kad 74
Soalan
PostgreSQL — customary default port and transport?
Jawapan
TCP 5432. PostgreSQL servers normally use it unless configured or compiled with another default.
Kad 75
Soalan
500/UDP — which IPsec setup protocol?
Jawapan
IKE, the Internet Key Exchange protocol. It negotiates IPsec security associations and commonly moves to UDP 4500 when NAT traversal is used.
Kad 76
Soalan
137/UDP — which NetBIOS service?
Jawapan
NetBIOS Name Service. It handles name registration and lookup in legacy NetBIOS over TCP/IP environments.
Kad 77
Soalan
SMTP message submission — normal port and transport?
Jawapan
TCP 587. It separates authenticated client submission from server-to-server SMTP relay on TCP 25; STARTTLS is commonly used.
Kad 78
Soalan
LDAP — conventional connection-oriented port and transport?
Jawapan
TCP 389. Connectionless LDAP can use UDP 389, and implicit-TLS LDAP commonly uses TCP 636.
Kad 79
Soalan
1701/UDP — which tunneling protocol?
Jawapan
L2TP. It tunnels Layer 2 traffic but needs a separate security layer such as IPsec when confidentiality is required.
Kad 80
Soalan
NetBIOS Datagram Service — common port and transport?
Jawapan
UDP 138. It provides connectionless NetBIOS datagram delivery.
Kad 81
Soalan
993/TCP — which mail-access service?
Jawapan
IMAPS. It begins IMAP with implicit TLS for encrypted access to mail stored on a server.
Kad 82
Soalan
LDAPS — commonly used implicit-TLS port and transport?
Jawapan
TCP 636. LDAP can instead use TCP 389 and negotiate TLS with StartTLS.
Kad 83
Soalan
PPTP control — port and transport?
Jawapan
TCP 1723. The control channel uses that port; PPP payloads travel through GRE, which is IP protocol 47 rather than port 47.
Kad 84
Soalan
139/TCP — which NetBIOS service?
Jawapan
NetBIOS Session Service. It historically carried SMB sessions; direct-hosted SMB commonly uses TCP 445 instead.
Kad 85
Soalan
POP3S — default port and transport?
Jawapan
TCP 995. It uses implicit TLS for encrypted POP3 mail retrieval.
Kad 86
Soalan
1812/UDP — which AAA service?
Jawapan
RADIUS authentication and authorization. RADIUS accounting normally uses UDP 1813.
Kad 87
Soalan
4500/UDP — which IPsec function?
Jawapan
IPsec NAT Traversal. It carries IKE and UDP-encapsulated ESP across network address translation.
Kad 88
Soalan
SIP signaling without implicit TLS — common port and transports?
Jawapan
UDP or TCP 5060. SIP over TLS conventionally uses TCP 5061, and media streams use separately negotiated ports.
88 kad
Common Network Port Numbers Flashcards: Protocols, TCP/UDP & Uses
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