Possible for opensips to sit behind a nat router on a lan and be able to simultaneously serve internal and external (routable) sip videoconferencing codecs?
I know the server should probably be in public addressable space, but in this instance we can't do that.
So can we have internal opensips with mediaproxy serving internal and external sip clients?
You can do that, by using the set_advertise_address() function (see http://www.opensips.org/Resources/DocsCoreFcn#toc139) - so even if listening on private interface, opensips will be able to advertise a public ip for traffic going into public side. Of course, you will need some port forwarding, so that traffic from public side will be received on internal net.