Disable SIP ALGs on Draytek Routers

Many commercial routers now a days are coming with SIP ALG`s turned on by default. This feature is suppose to help with Nat related issues but in majority it break the implementation and cause issues such as one way audio, lack of incoming calls, registration issues and etc.

Recently, We have received couple of calls regarding IP phones not working behind DreyTek routers. The reason is same SIP ALG.

If you are a victim of this feature please disable it using the following procedure.

Telnet into the router and enter the following command.

1. > sys sip_alg 0 — Disables sip alg

2. > sys commit — Apply changes

3. > sys reboot — Reboot router

Once router is back online, reboot the ip phone or press re-register.