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