SIP ALG is a setting found in many commercial and residential firewalls, routers, or modems. It is a tool that inspects SIP messages which are used in VoIP phones and transforms these messages. This can cause a number of issues on the network.
Common symptoms of SIP ALG
Some of the most common symptoms of SIP ALG are listed below:
- One-way or No-way audio, this can be intermittent or consistent
- Outbound or inbound calls fail to connect
- Audio cuts out completely while on a call and doesn't return
- Phones continue to ring and cannot be answered.
- The inability to call another extension on the network
- Busy Lamp Field keys acting slow or not working at all.
How to turn off SIP ALG
While the symptoms of SIP ALG can be easy to detect, it may not always be easy to turn off, this is due to the location of these settings and how they differ from each manufacturer. Some routers that we have come across have been listed below with steps on how to remove this:
- Logon to the Huawei HG659 Web interface using your favourite web browser (by default this should be http://192.168.1.1)
- Enter the administration username and password for your router provided by your Internet provider.
- Once you have logged into the router, in the top menu click "Internet" then in the left hand menu click on "Forwarding"
- Expand the "ALG" menu and from there ensure that "Enable SIP ALG" is un-ticked and then click on "Save"
- If needed, you can also change the firewall level to low (from a choice of off, low, or high)
- In the top menu, click on "Internet" then "Network Security"
- Under Firewall, change the security level to "low"
- Click on "Save"
DrayTek Vigor (firmware 3.8.5 and newer)
- Using your favourite web browser log into the DrayTek vigor router (The default IP address is 192.168.1.1) and the default username is admin, the default password is admin
- On the left hand menu, expand the "NAT" menu
- Click on "ALG"
- Uncheck "Enable ALG" to disable the feature
- Click "Ok"
TP-Link Archer VR1600v
- Using your favourite web browser navigate to 192.168.1.1 (the default IP address for the router) the default username and password is admin however, if this is in default mode it will require you to set up a new access password.
- In the top menu select the "Advanced tab", then "NAT Forwarding" on the left hand menu
- Select "ALG"
- Uncheck "SIP ALG" to disable this feature
- Click on "Save"