How to disable SIP ALG for an ASUS Router

Note: that this process will reboot your router - which will temporarily take your internet connection and phone service offline. 

We recommend doing this in an off-peak period or outside of business hours.

Disabling SIP ALG for an ASUS Router

Log into your router's web interface, then select WAN > NAT Passthrough

Locate the SIP Passthrough option and choose Disable. Click Apply and, if prompted, restart your router.