The AT&T 2wire router will not let you turn off SIP ALG. It doesn’t even have that setting listed. The problem is that SIP ALG means that the router is cleaning up the SIP packets and we don't want anything to mess with the packets. It causes problems that show up in various ways such as: Your phone might not be able to register with the phone system, really bad jitter in phone conversations (usually on the caller side), or other issue.
You need to put your AT&T Uverse (2Wire) router into Bridge mode (IP Pass Through) and connect it to your own router…a router that lets you turn off SIP ALG.
Putting your 2wire into bridge mode tells your 2wire to pass all traffic to your own router without doing anything to the traffic. Your router will manage your network. Again, turn off SIP ALG in your router.
Browse to your 2wire (192.168.1.254) and do the following:
- Click Settings and then Event Notifications
- Check the box labeled “Router behind Router”
- Click [Save]
Plug a CAT5e cable into the 2wire (port 4) and the other end into your Router (Internet port). You can still browse to 192.168.1.254 even if your router gives other IP address scheme.