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