sending snmp request to same link

Does the poller have a private address? This should be a relatively easy iRule

when CLIENT_ACCEPTED { 
      if [IP::addr [IP::client_addr]] eq x.x.x.x { 
 snatpool y.y.y.y 
 pool z.z.z.z } }

where x.x.x.x is the IP of the poller, y.y.y.y is the snatpool containing a snat on the 12.239.13.1 network (or maybe use automap if you have a selfip there), and z.z.z.z is a pool that only contains the router 12.239.13.1.