Simple Network Management Protocol (SNMP) is a networking protocol used for the management and monitoring of network-connected devices in Internet Protocol networks. The SNMP protocol is embedded in multiple local devices such as routers, switches, servers, firewalls, and wireless access points accessible using their IP address. SNMP provides a common mechanism for network devices to relay management information within single and multi-vendor LAN or WAN environments. It is an application layer protocol in the OSI model framework.
Typically, the SNMP protocol is implemented using the User Datagram Protocol (UDP). UDP is a connectionless protocol that works like the Transmission Control Protocol (TCP) but assumes that error-checking and recovery services are not required. Instead, UDP continuously sends datagrams to the recipient whether they receive them or not.
SNMP Management Information Bases (called MIBs for short) are data structures that define what can be collected from the local device and what can be changed and configured. There are many MIBs defined by standards bodies such as the IETF and ISO, as well as proprietary MIBs defined by specific IT equipment vendors such as Cisco and software vendors such as Microsoft and Oracle.
There are three different versions of SNMP:
SNMP version 1 (SNMPv1)—This was the first implementation, operating within the structure management information specification, and described in RFC 1157.
SNMP version 2 (SNMPv2)—This version was improved to support more efficient error handling and is described in RFC 1901. It was first introduced as RFC 1441. It is often referred to as SNMPv2c.
SNMP version 3 (SNMPv3)—This version improves security and privacy. It was introduced in RFC 3410.
SNMP version 2 is the most commonly deployed SNMP protocol version today. The most recent version, SNMP version 3, includes new security features that add support for authentication and encryption of SNMP messages as well as protecting packets during transit.
What is an SNMP port?
SNMP ports are utilized via UDP 161 for SNMP Managers communicating with SNMP Agents (i.e. polling) and UDP 162 when agents send unsolicited Traps to the SNMP Manager.
Get Request—A request to retrieve the value of a variable or list of variables.
Set Request—Sent by the SNMP manager to the agent to issue configurations or commands.
GetNext Request—Sent by the SNMP manager to agent to find the values of the next record in the MIB’s hierarchy.
GetBulk Request—Sent by the SNMP manager to the agent to obtain large tables of data by performing multiple GetNext Request commands.
SNMP Response—Sent by the agent to the SNMP manager, issued in reply to a
SNMP Trap—Asynchronous trap messages from SNMP agents alert an SNMP manager that a significant event such as an error or failure, has occurred.
SNMP Inform—Confirms receipt of a trap.