What is SIP ALG?

What is SIP ALG?

SIP ALG or firewall on the router

SIP ALG stands for Application Layer Gateway and is common in many commercial routers.
  • SIP ALG (Also called SIP PASS THROUGH or SIP HELPER) was invented to get around NAT problems by rewriting some packets.
  • Unfortunately, SIP is rather complicated, and most SIP ALG implementations are horribly broken. (Netgear, Dlink, Zyxel).
  • If you experience missing audio, failing registrations, failed calls, failed video calls, or failed transfers, please verify that your router does NOT use SIP ALG and disable SIP ALG if it does.
  • If you are unable to change the router configuration, try using TLS encryption (if the SIP server supports it) to encrypt the traffic and stop the router from tampering with the packets.
Disable SIP ALG in the router - Your Internet Service Provider should assist in this Regard
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