Protocols and Ports
Protocols and Ports
A protocol is a set of rules that devices follow to communicate over a network. Protocols define how data is formatted, transmitted, received, and processed.
TCP/IP Protocol Suite
These are the foundation of the Internet.
Protocol Purpose PortIP Addressing and routing N/A
TCP Reliable communication N/A
UDP Fast, connectionless communication N/A
ICMP Network diagnostics (ping) N/A
ARP Resolves IP to MAC addresses N/A
IPv4 32-bit addressing N/A
IPv6 128-bit addressing N/A
Web Protocols
Protocol Purpose PortHTTP Web browsing 80
HTTPS Secure web browsing 443
WebSocket (WS) Real-time web communication 80
WebSocket Secure (WSS) Secure real-time communication 443
Example:
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https://www.microsoft.com
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Uses HTTPS on Port 443.
File Transfer Protocols
Protocol Purpose PortFTP File Transfer 20, 21
FTPS Secure FTP 990
SFTP Secure File Transfer (SSH) 22
TFTP Simple File Transfer 69
Used for:
File uploads
Backups
Device configuration files
Email Protocols
Protocol Purpose PortSMTP Send email 25, 587
POP3 Download email 110
POP3S Secure POP3 995
IMAP Synchronize email 143
IMAPS Secure IMAP 993
Name Resolution Protocols
Protocol Purpose PortDNS Domain Name Resolution 53
mDNS Multicast DNS 5353
LLMNR Local Name Resolution 5355
Example:
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google.com → 142.250.x.x
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DNS performs this conversion.
Remote Access Protocols
Protocol Purpose PortSSH Secure Remote Administration 22
Telnet Remote Administration (Insecure) 23
RDP Remote Desktop 3389
VNC Remote Desktop Access 5900
Network Management Protocols
Protocol Purpose PortSNMP Network Monitoring 161/162
Syslog Log Collection 514
NetFlow Traffic Analysis Varies
Used by network administrators.
Address Assignment Protocols
Protocol Purpose PortDHCP Automatic IP Assignment 67/68
DHCPv6 IPv6 Address Assignment 546/547
Provides:
IP Address
Gateway
DNS Server
Security Protocols
Protocol Purpose PortTLS Encryption Various
SSL (Legacy) Encryption Various
IPsec VPN Security Various
Kerberos Authentication 88
LDAP Directory Services 389
LDAPS Secure LDAP 636
RADIUS Authentication 1812/1813
TACACS+ Device Authentication 49
Wireless Protocols
Protocol Purpose802.11a Wi-Fi
802.11b Wi-Fi
802.11g Wi-Fi
802.11n Wi-Fi 4
802.11ac Wi-Fi 5
802.11ax Wi-Fi 6
WPA2 Wireless Security
WPA3 Wireless Security
Routing Protocols
Used by routers to learn network routes.
Protocol PurposeRIP Distance-vector routing
OSPF Link-state routing
EIGRP Cisco routing protocol
BGP Internet routing
IS-IS Service provider routing
Voice and Video Protocols
Protocol PurposeSIP VoIP Call Setup
RTP Voice/Video Delivery
RTCP RTP Monitoring
H.323 Voice/Video Communications
Network Time Protocols
Protocol Purpose PortNTP Synchronize time 123
PTP Precision Time 319/320
VPN Protocols
Protocol PurposePPTP Legacy VPN
L2TP VPN Tunneling
IPsec Secure VPN
SSL VPN Browser-based VPN
OpenVPN Secure VPN
WireGuard Modern VPN
Common Ports to Memorize for Network+
Protocol and Port NumberFTP 20, 21
SSH 22
Telnet 23
SMTP 25
DNS 53
DHCP 67, 68
TFTP 69
HTTP 80
POP3 110
NTP 123
IMAP 143
LDAP 389
HTTPS 443
SMB 445
Syslog 514
LDAPS 636
FTPS 990
IMAPS 993
POP3S 995
RDP 3389
Network+ Exam Memory Trick
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20/21 = FTP
22 = SSH
23 = Telnet
25 = SMTP
53 = DNS
67/68 = DHCP
80 = HTTP
110 = POP3
123 = NTP
143 = IMAP
389 = LDAP
443 = HTTPS853 = DNSSEC
3389 = RDP5900 = VNC
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Simple Definition
A network protocol is a standardized set of rules that enables computers, servers, routers, switches, and other devices to communicate, exchange data, and provide services across a network or the Internet.
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