[SR-Users] Kamailio does'nt respond to packets from specific addresses

Hi everyone, I have the following problem: I have a Kamailio server that is connected to several Asterisk servers for load balacing in a LAN network with the IP's of 192.168.16.X. I recently connected with another company that is supposed to send me calls through the Kamailio server. The problem is this: I am connected to then with a cable from their network to mine. My port has the address 10.9.18.198 and they come from the address 172.18.177.18. When I get packets from their address (172...) I can see them getting to my Kamailio server, but the Kamailio does not respond. It only happens when I get packets from 172 source address. If I get from 192 or 10 adresses from my LAN network it works, and if I get packets from real world IP's through my WAN it works. Does anyone have any idea why the Kamailio does'nt respond to packets from 172 adresses? And how to fix this? Thanks in advance!