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