IT Protocols

DNS

Finds the Ip address associated with a registered internet domain. Port 53. Mostly UDP, TCP

HTTP

A protocol used for transferring hypertext requests and information on the internet, port 80. TCP

HTTPS

A secure version of HTTP that uses encryption to protect data exchanged over the internet, port 443. TCP

SMTP(Simple Mail Transfer protocol)

A protocol used for sending emails from clients to an email server, port 25. TCP

POP3

A protocol used for retrieving emails from a mail server, port 110. TCP

IMAP(Internet Message Access Protocol)

A protocol used for accessing and managing emails on a mail server, allowing for multiple device access, port 143(Unencrypted) 993(SSL/TLS). TCP

LDAP(Lightweight Directory Access Protocol)

A protocol for accessing and maintaining distributed directory information services, commonly used for authentication and directory lookups, port 389. TCP

SSH(Secure Shell)

Provides a strong authentication and encrypts data transport between client and remote computer. port 22. TCP

Telnet

Insecure remote access protocol that provides command line on a remote computer/legacy. port 23. TCP

RDP

A protocol used for remote desktop access to Windows machines, allowing users to connect and control a remote computer. Port 3389. TCP

DHCP(Dynamic Host Configuration)

Protocol that automatically assigns IP addresses and other network configuration parameters to devices on a network. Port 67 for server, port 68 for client. UDP

NetBIOS

Provides a system for older computer applications to communicate between devices on a LAN. Port 137-139. TCP/UDP

SNMP(Simple Network Management Protocol)

Enables network admin to monitor network operations from centralized monitoring stations. Port 161 for general use, port 162 for traps. UDP

SLP(Service Location Protocol)

A protocol that allows devices to discover services in a local area network. port 427. Usually UDP, but can use TCP.

SMB(Server Message Block)

A network file sharing protocol that allows applications to read and write to files and request services from server programs. Port 445. UDP/ TCP.

FTP

A standard network protocol used for transferring files between a client and a server on a computer network. port 20 for data transfer, Port 21 for control. TCP.

TFTP(Trivial)

FTP with minimal overhead. No authentication. Used for booting network devices or transferring config files. Port 69. UDP.

CIFS/SMB

A set of network protocols that enables file sharing, printer sharing, and access to remote services. Port 445, using both TCP/UDP.

AFP

Apple file protocol used for macOS. Port 548. TCP, UDP

SFTP

Provides secure file transfers over SSH. Encrypts both authentication and data. Port 22

FTPS(FTP Secure)

Encrypts both authentication and data. That adds a layer of encryption using SSL/TLS. Port 990(Implicit TLS), 21(Explicit TLS)

NTP(Network Time Protocol)

Synchronizes the clocks of computers and devices on a network to a standard time source. Port 123. UDP

ICMP(Internet Control Message Protocol)

Delivers control and error messages across IP networks.

SIP (Session Initiation Protocol)

Used to initiate, maintain, and terminate VoIP calls. Port 5060(Unencrypted), 5061 (Encrypted)

IGMP (Internet Group Management Protocol)

Used to manage multicast group memberships for IPv4 networks. Works alongside multicast routing protocols.(Layer 3 Protocol)

OSPF (Open Shortest Path First)

Link-state routing protocol used internally within larger enterprise networks. Dynamically finds the shortest path. (IP Port 89)

EIGRP (Enhanced Interior Gateway Routing Protocol)

Cisco proprietary hybrid routing protocol combining features of link-state and distance-vector protocols.It allows for efficient routing in large networks and uses a metric based on bandwidth and delay. IP protocol 88

L2TP(Layer 2 Tunneling Protocol)

Used to support VPNs by tunneling traffic over the internet. Usually combined with IPsec for encryption. Port 1701

IPsec (Internet Protocol Security)

Provides secure IP communications by authenticating and encrypting each IP packet in a communication session.Often for VPNs. Uses ESP (IP protocol 50) and AH (IP protocol 51)

TACACS+ (Terminal Access Controller Access-Control System Plus)

Cisco proprietary protocol that provides centralized authentication for users accessing network devices. Port 49.

RADIUS (Remote Authentication Dial-In User Service)

Provides centralized AAA (Authentication, Authorization, and Accounting) management for users connecting to a network service. Port 1812 (authentication), 1813 (accounting)

RIP (Routing Information Protocol)

Distance-vector routing protocol used in small networks. Uses hop count as a metric with a maximum of 15 hops. Periodically broadcasts routing tables. UDP Port 520

LACP (Link Aggregation Control Protocol)

Part of the IEEE 802.3ad standard allows multiple physical links to be combined into a single logical link to increase bandwidth and provide redundancy. It automatically negotiates and manages these aggregated links between devices like switches.

FHRP (First Hop Redundancy Protocol)

A category of protocols that provide gateway redundancy for hosts on a subnet. If the primary router becomes unavailable, a backup router takes over, ensuring uninterrupted network access.

HSRP (Hot Standby Router Protocol)

Cisco's proprietary FHRP provides router redundancy by creating a virtual IP address. Only the active router handles traffic. Ip protocol 112

VRRP (Virtual Router Redundancy Protocol)

Open standard FHRP similar to HSRP. One router (the master) responds to traffic; backups take over if the master fails. IP protocol 112

GLBP (Gateway Load Balancing Protocol)

Cisco proprietary protocol offering both redundancy and load balancing across multiple gateways. IP protocol 124

STP (Spanning Tree Protocol)

Prevents loops in Ethernet networks by logically blocking redundant paths. Ensures there’s only one active path between two network devices.

LLDP (Link Layer Discovery Protocol)

Allows network devices to advertise identity and capabilities on a local network. Used for network mapping. Vendor Neutral. Layer 2 Protocol

CDP (Cisco Discovery Protocol)

Cisco proprietary version of LLDP. Helps identify directly connected Cisco devices. Layer 2.

NDP (Neighbor Discovery Protocol)

Replaces ARP in IPv6. Also handles router discovery, address autoconfiguration, and reachability. Layer 3

Syslog

Standard for sending log and event messages to a central logging server. Port 514 UDP

TLS (Transport Layer Security)

Cryptographic protocol that provides encryption, integrity, and authentication for data transmitted over a network.

NetFlow

Network protocol developed by Cisco for collecting IP traffic information. It helps in traffic analysis and monitoring.

BGP(Border Gateway Protocol)

The protocol used to exchange routing information between different autonomous systems on the internet, enabling efficient data packet routing.