ipMonitor likely did not get a response via SNMP when you were performing a scan of those devices. Are you certain that SNMP connections work from the ipMonitor host to the firewall devices?
I would try by adding a SNMP monitor manually in ipMonitor to the device and seeing if that works. If it does not it may be that the devices do not have SNMP enabled, are using incorrect community or are not responding to the ipMonitor server do to some configuration reason.
You can also use the SNMP Monitor wizard under the configuration tab of ipMonitor to try and walk the firewall devices. Try a OID such as 188.8.131.52 so that it will walk all the OID's available.
Hope this helps!
Normally on a Cisco PIX and ASA SNMP queries are locked down based on IP address. So within the ASA and PIX config, you need to add your IP address of your ipMonitor server. Something like: snmp-server host inside xxx.xxx.xxx.xxx community public (or whatever your readonly string is).
We have a CISCO-AS5520 Firewall. I have a SNMP Version 2 monitor build with the "number of active connections" as follows:
UDP Port = 161
OID = 184.108.40.206.220.127.116.11.418.104.22.168.6.0
Analyze the Result as: Numeric data < 3000
The monitor is down when we have more then 3000 firewall connections from the intranet nic.