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Turn Off SIP ALG on TP-Link Router
SIP ALG is a feature found in most network routers, it operates as a function of the firewall. It consists of two different technologies:
- Session Initiation Protocol (SIP) – The underlying service that powers all Voice over Internet Protocol (VoIP) phones, apps, and devices. SIP manages registering devices, maintaining call presence, and overseeing the call audio.
- Application Layer Gateway (ALG) – Routers segment your ISP and your internal network through a process known as Network Address Translation (NAT). An ALG acts as a proxy to rewrite the destination addresses in data packets for improved connectivity.
In a few situations, this can be useful, but in most situations, SIP ALG causes problems with the voice service. Very often, SIP ALG causes VoIP messages to be modified in a harmful way or simply corrupt them. In such cases, you may experience issues such as, registering your handset, one-way or no audio, dropped calls and being unable to receive calls at all.
In TP-Link Routers SIP ALG is enabled by default, we recommend disabling it.
The following example is the Archer VC series routers.
1. Open up a browser (Firefox, Chrome etc) and go to 192.168.1.1 (this is the default IP address) The default username is admin and the default password is admin

Other TP-Link Models
Deco series

VR Series

TD Series
