The Service port acts as a DHCP server, and has its own dedicated IP range (192.168.125.*, IIRC). This is not compatible with a 10.anything IP range.
Also, the Service port acts as a DHCP server. If the router is also acting as a DHCP server, they are probably in conflict.
The Service port is intended for direct, local connection, not for connection to larger networks. The internal network for the Service port also supports several devices internal to the IRC5, which is another potential source of conflict. Connecting the Service port to a larger, complex network is, as far as I know, not advised.
Possibly, this might work if you used a dedicated port on the router, and set forwarding rules in the router to segregate IRC5 traffic from any other traffic. But that would take more networking knowledge than I have, as well as depending on the capabilities of the specific router you are using.
My service port is configured statically at 192.168.125.1. Yes, the port has the possibility of DHCP, but we do not use it.
You are right, you can make friends of these networks only by waking up ports and masquerading packets. It was organized but still there are some communication problems. I suspect that there are some ports that are being blocked by the firewall or that I have missed. Although there are not so many of them:
UDP - 5512, 5513, 5514
TCP - 5515, 21