Sometimes ALG (Application Layer Gateway) can cause problems with VoIP.

ALG is often enabled on newer routers and can affect SIP (Session Initiation Protocol).

If you have a Draytek router you can disable ALG but have to do this via Telnet.

Once conencted via Telnet check the ALG status by typing in:-


sys sip_alg ?



If it is enabled you can disable it and restart the router by issuing the following commands:-

sys sip_alg 0
sys commit
sys reboot