Is SIP ALG broken on ZyWall VPN 300?
Contrary to all recommendations, I have experienced, that I must activate SIP ALG in order to have my phones working behind our ZyXEL VPN 300. However, whenever I switch the ZyXEL off and turn it back on the phones will not work until I've manually disabled SIP ALG (+ Apply) followed by enabling SIP ALG (+ Apply). Why is this? Can I flick a switch somewhere to correct this bad behavior?