Disable SIP ALG

SIP ALG is a software layer gateway that manages protocols such as SIP and FTP. SIP ALG can ensure and check whether traffic passes through the gateway or not. The protocol intercepts packets and checks them, and depending on the approval, the packet either passes through the gateway or not.

When using a hosted VoIP solution, SIP trunk, or other solutions that use SIP, SIP ALG is usually not useful.

Why not? Because it checks whether the packets are allowed through the gateway, right? That’s exactly the problem. If it can’t get through the gateway, the packet is dropped, preventing a call or similar from being established.

So that’s a problem. Are there other protocols like this besides SIP ALG? A SIP Helper does pretty much the same thing and is therefore comparable.

But how does the telephone exchange know whether the packets are allowed through? All packets are sent to the internet by the router. If SIP ALG is enabled, the ALG tries to route the packets in the right direction, which is exactly what a telephone exchange does not want!

How can I disable SIP ALG?

SIP ALG can be disabled in the following ways:

DRAYTEK

·       NAT

·       ALG

·       Vink ‘enable ALG’ uit

CISCO

·       Configure terminal

·       No ip nat service sip udp port 5060

·       No ip nat service sip udp port 5080

·       Write

MIKROTIK

·       /ip firewall service-port

·       Set sip disables=yes

UBIQUITI EDGEMAX

·       Configure

·       Set system conntrack modules sip disable

·       Commit

·       Save

·       Exit

NETGEAR

·       Login

·       Advanced

·       Setup

·       WAN setup

·       Disable SIP ALG