Template:FAQ:Applications 13

There is one final possibility to consider for why a SET request might be rejected.

The values for certain MIB objects (including 'sysLocation' and 'sysContact') can be configured via the 'snmpd.conf' file. If this is done, then these particular objects become read-only, and cannot be updated via SET commands, even if the access control settings would otherwise allow it.

This may seem perverse, but there is good reason for it. If there is a configuration setting for one of these objects, then that value will be used whenever the agent re-starts. If the object was allowed to be updated using SET, this new value would be forgotten the next time the agent was re-started.

Hence the Net-SNMP agent rejects such requests if there's a value configured via the 'snmpd.conf' file. If there isn't such a config setting, then the write request will succeed (assuming suitable access control settings), and the new value will be retained the next time the agent restarts.