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Zyxel Zywall USG 100/200

This guide explains, how to configure a Zyxel Zywall USG series firewall in order for it to operate normally when using our VoIP services.

Deactivate SIP-ALG

The first step is to deactivate the SIP-ALG feature in the router settings. For this you will have to log in into your USG router.

Go to the configuration tab (The icon with two wheels on the left).

Within the configuration menu, click on “ALG”.

Uncheck the “Enable SIP ALG”“Enable SIP Transformations” and “SIP inactivity Timeout” parameters.

Enable telnet access

In order to set the UDP timers (step 3), you first need to activate telnet access in your router.

To enable telnet, go to the configuration tab, within the configuration menu, click on “TELNET” and simply check the option “Enable”.

After the changes are made you can restart the router.

Set UDP timers

For this step you will need a telnet client, try to search for telnet on your PC. (Press start button, and search for “telnet”). If nothing shows up it means that your windows version doesn’t include Telnet, if that is the case, download PuTTy, which is a free telnet client.

For Mac OS X users

Open a terminal, (Search for “terminal” in spotlight), and type : telnet ip_address_of_your_router 23

For Windows users (w/PuTTy)

  1. Launch PuTTy
  2. Select the “telnet” option
  3. Enter the ip of your router and click on the connect button

For Windows users (w/Microsoft Telnet)

  1. Press CTRL-R, type in “cmd”, this will open up a new console window
  2. In the window, type : telnet ip_address_of_your_router 23

Once the connection is made, the router will prompt for your username and password. Enter your credentials and hit enter.

Type in the following commands after the authentication :

 configure terminal
 show session timeout udp
 session timeout udp-connect 300
 session timeout udp-deliver 300
 show session timeout udp

Restart your router after the changes are made.