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