SIP ALG Test
Test whether your router’s SIP ALG rewrites phone calls. SIP ALG is a common cause of one-way audio, phones losing registration and dropped calls.
What the Test Does
The test sends a real SIP message to the test server and compares what arrived with what was sent. If a router rewrote it on the way, the test shows the changed lines. A browser cannot send SIP, so the test runs in a small app.
Should SIP ALG Be On or Off?
Off, for almost every hosted phone system and SIP trunk. Leave it on only if your phone provider asks you to.
Run the Test
Windows (Intel and AMD)
Double-click the downloaded file. It runs the SIP test on its own, in about five seconds.
macOS
Open the disk image and double-click the SIP Test app. It runs the SIP test on its own, in about five seconds.