Is it possible to manipulate the pings (OPTIONS in my case) to force a source ip:port combo per destination?

dispartcher.list: 1 sip:192.168.0.1:5060 2 sip:192.168.1.1:5070 3 sip:192.168.2.1:5050

The kamailio (4.1) is listening on 192.168.3.1 5060 and 5070. dispatcher 2 cares about the source port, which should be 5070. 1 and 3 don't care.