This has come up before, but with different versions of their modem/router. I just switched to this service, and have modem model 3800HGV-B. I have TV, internet and phone service through the one box. I cannot get the RRC's to connect through it. It was all working with my Time Warner service. I am changing services to get lower latency, which the ATT service does provide. I was have a lot of trouble with CW transmit errors, as I reported in another thread.
I have changed the SIP port to 5080, and set up the router for pinholes for 5080 (SIP), 11000 (UDP), and 12000 (UDP).
The router has only one entry for each; rather than separate entries for In/Out etc. Oddly, the 12000 port is listed on one status page as TCP; on the setup paged as UDP, regardless of how many times I re-enter.
I have checked, rechecked all IP addresses; and reconnected with old Time Warner service which I also still have (it connects).
Any suggestion?