Simple Network Management Protocol (SNMP) is a protocol for gathering data about the operation of networking devices. The protocol has undergone three major revisions to enhance functionality and security. The basic premise of SNMP is to use a Management Information Base (MIB) to GET or SET parameters within the device.
A MIB provides a format for getting the data and is configured in tree like structure.
There is a very nice MIB navigator at Cisco SNMP Object Navigator
A Network Management Station (NMS) or device would conduct an snmpwalk to gather data via a poll of the network device. The request (POLL) was verfied by a password known as a community string. The community string is actually a password with either read-only privileges (GETs only) or read-write (GETs and SETs). SNMP has three versions-
- SNMPv1 Community String was in the “Clear”/ unencrypted
- GET gathers information based on the Object ID (OID) from the MIB
- GETNEXT iterative requests to gather OID info
- SET define the parameter based on the Object ID
- TRAP send unsolicited information to the Network Monitoring Device
- SNMPv2c enhanced efficency, but still lacked security
- GETBULK allows for a single poll to gather several GET
- INFORM response to TRAP from NMS
- SNMPv3 enabled security with both Authentication and Privacy based on a User-based Security Model (USM)
- NoAuthNoPriv Communication without authentication and privacy
- AuthNoPriv Communication with authentication and without privacy
- AuthPriv Communication with authentication and privacy
NEXT-> How do you Configure SNMP?