ARP via SNMP from Cisco FWSM? It's less common than you think

If you want to get ARP entries out of a Cisco Firewall Service Module, forget about SNMP. You can't. Cisco didn't include the MIB to let you pull that data. You'll need to script something using "expect" or other language to go in and pull it out via the CLI. Rumors are Cisco will support ARP via SNMP in a future software release. Let's hope so.