Ping but no SNMP - Alarms in Cisco Prime Infrastructure 3.0

[GirvanMcD]

Good day all.  From Cisco Prime Infrastructure 3.0. I receive this Alarm, "Condition:Device SNMP unreachable, ICMP pingable" and in less than ten minutes another report shows that it is reachable.  What could be the cause for the server to be able to ping but snmp unreachable?

[Alexander Jelinek]

Moved this to the Network Management Community

[david.johnson]

Did you ever figure this out? I'm currently dealing with this issue myself, receiving up to 300 alerts a week on the same 8 branch switches.

[Craig Budrodeen]

If ICMP works but SNMP doesn't then it won't be the routing.

Check to see if your SNMP target is enabled for all versions of SNMP, especially 1 and 2c, and that your SNMP poller knows what version of the protocol is being used.
Check to see that the community string in the config matches the community string being sent by the poller.
If you are using v3 make sure all auths are correct.
If the target device is a server, make sure the snmpd service is running (Linux) or the SNMP Agent Service is enabled in Administrative Tools (Windows)
If the target is a router then make sure that there is no ACL applied to the RO string in the config - if it is add the polling server address
Before you check any of that, make sure any interceding firewall is not dropping snmp packets (UDP 161) by inspecting the logs.