Does anyone know if there is a standard or Cisco MIB branch that would give me the size (number of entries) in the current routing table? I need to be able to monitor it via a simple SNMP poll. I know I could do it with a newer embedded events manager and the ability to update the MIB from the output of "show ip route sum" but I'm looking for a simpler solution.
Actually, you don't need EEM for this. You can use the EXPRESSION-MIB by itself to count the number of routers in the table. See this thread for an example of how to count the number of entries in a table:
The table in your case is the ipRouteTable. The best object to count in this table is ipRouteDest.