- SIP ALG is enabled by default and must be disabled to prevent issues with VoIP phones.
- DNS DHCP servers need to be set to efficient DNS servers to prevent registration issues with Polycom phones.
- Log in to the router's web user interface.
- Click on Firewall -> Firewall Advanced
- Set SIP ALG to "Off"
- Contact AT&T and tell them that you want the DHCP DNS servers on their AT&T modem changed to Google's public DNS:
- Primary DNS server: 188.8.131.52
- Secondary DNS server: 184.108.40.206