Essential SNMP

Appendix F. SNMPv3

Security has been the biggest weakness of SNMP since the beginning. Authentication in SNMP Versions 1 and 2 amounts to nothing more than a password (community string) sent in clear text between a manager and agent. Any security-conscious network or system administrator knows that clear-text passwords provide no real security at all. It is trivial for someone to intercept the community string, and once he has it, he can use it to retrieve information from devices on your network, modify their configuration, and even shut them down.

The Simple Network Management Protocol Version 3 (SNMPv3) addresses the security problems that have plagued both SNMPv1 and SNMPv2. For all practical purposes, security is the only issue SNMPv3 addresses; there are no other changes to the protocol. There are no new operations; SNMPv3 supports all the operations defined by Versions 1 and 2. There are several new textual conventions, but these are really just more precise ways of interpreting the datatypes that were defined in earlier versions.

This appendix provides an introduction to SNMPv3 and covers SNMPv3 configuration for a Cisco router and the Net-SNMP agent. Although SNMPv3 is not yet a full standard, a few vendors sell products with SNMPv3 support. We chose to cover two popular SNMPv3 implementations for our configuration examples.

Changes in SNMPv3

Although SNMPv3 makes no changes to the protocol aside from the addition of cryptographic security, its developers have managed to ...