This can give you unexpected behaviour, such as phones not registering and incoming calls failing. SIP ALG modifies SIP packets in unexpected ways, corrupting them and making them unreadable. How can it affect VoIP?Įven though SIP ALG is intended to assist users who have phones on private IP addresses (Class C .X), in many cases it is implemented poorly and actually causes more problems than it solves. What is SIP ALG SIP ALG stands for Application Layer Gateway and is common in all many commercial routers.
A NAT router with a built-in SIP ALG can re-write information within the SIP messages (SIP headers and SDP body) making signalling and audio traffic between the client behind NAT and the SIP endpoint possible. Go to the Firewall tab Click Settings Set SIP to Off Set H.323 to Off Disabling SIP ALG for Ubiquiti EdgeRouter (EdgeMax CLI/Command Line Interface) You can perform this change from the command line by logging in, then entering the following commands: from ssh#ENABLE SIP ALG SERIES#
If the SIP proxy doesn't provide a server-side NAT solution, then an ALG solution could have a place.Īn ALG understands the protocol used by the specific applications that it supports (in this case SIP) and does a protocol packet-inspection of traffic through it. Use this guide to configure and monitor application layer gateway (ALG) on NFX Series and SRX Series Firewalls to manage application protocols such as H.323, FTP, Session Initiation Protocol (SIP), and ICMP. In some scenarios, some client-side solutions are not valid, for example, STUN with symmetrical NAT router.
Generally speaking, ALG works typically in the client side LAN router or gateway. There are various solutions for SIP clients behind NAT, some of them in the client side (STUN, TURN, ICE), others are in the server side (Proxy RTP as RtpProxy, MediaProxy). Many routers have SIP ALG turned on by default. It is a security component of a router, or NAT, that allows VoIP traffic to pass back and.
Its purpose is to prevent some of the problems caused by router firewalls by inspecting VoIP traffic (packets) and if necessary modifying it. First, a little background on SIP ALG (Application Layer Gateway). SIP ALG stands for Application Layer Gateway and is common in all many commercial routers.
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