I recently troubleshot a problem with Ekiga 3.2.7 running on Ubuntu 10.10 x86. The application could not successfully make a test call with full two way audio; audio from the far end was not successfully received.
Looking back through the Ekiga list archives revealed at least one other user with similar problems on this model of router:
The solution in my case was to simply assign the host problem system a fixed IP address, and set up a port forwarding rule in the router thusly:
Test calls could then be made okay.