{{tag>Troubleshooting Broadband_Routers Firewall NAT DrayTek Vigor}}
====== How to Adjust NAT Session Timeout on DrayTek Vigor Models ======
When your handset send a message to our Hosted VoIP platform your DrayTek router will translate the internal IP address to an external IP address and maintain this translation for a predetermined length of time. If this expiry time occurs before your handset sends another message (such as a keep-alive) then the translation will be removed and you will experience incoming call failures and [[features:blf|BLF]] will no longer function.

Very often security appliances will set a NAT session timeout to a very low value, which will interfere with VoIP. We recommend the UDP timeout is set to 300 seconds (5 minutes) at the least.

This guide explains how to check and adjust the NAT session timeout value on the following DrayTek models:
  * **Vigor 2760**
  * **Vigor 2800**
  * **Vigor 2820**
  * **Vigor 2830**
  * **Vigor 2832**
  * **Vigor 2860**
  * **Vigor 2862**
  * **Vigor 2920**
  * **Vigor 2925**
  * **Vigor 2926**
  * **Vigor 2952**
  * **Vigor 2960**

Even if your particular DrayTek model is not listed, these instructions should still apply if your model is in the same series.

===== Step-by-Step Guide =====
  - Press the Windows Start button and in the search box type in **cmd** and hit //Enter//
  - Type in\\ <code>telnet 192.168.1.1</code> and hit //Enter//\\ //**Note** Recent versions of Microsoft Windows  may not have **Telnet** installed by default.\\ To install Telnet, click on **Start -> Control Panel -> Programs -> Programs and Features -> Turn Windows Features on or off** -> Ensure **TELNET CLIENT** is checked and click OK.//
  - When prompted, enter your router username and password.\\ //The default username is **admin** and the default password is **admin**//
==== Checking NAT timeout value ====
  - Type in\\ <code>portmaptime -l </code>and hit //Enter//
  - Note the //UDP Timeout//

==== Adjusting NAT timeout value ====
If you need to change the timeout value...
  - To set the new timeout value type in\\ <code>portmaptime -u 300</code> and hit //Enter//\\ We recommend a value of at least 5 minutes (300 seconds)
  - To confirm the setting type in\\ <code>portmaptime -l </code>and hit //Enter// 
  - To save the change type in\\ <code>sys commit</code>and hit //Enter//

===== Notes =====
Do not adjust your IP phone keep-alive interval to a value below 30 seconds. Our network may block SIP traffic that is too frequent which will affect phone calls and BLF. 

====== See Also ======
  * [[troubleshooting:sip_alg:draytek]]

====== Further Reading ======
[[https://www.draytek.co.uk/support/guides/kb-portmaptime|NAT on DrayTek Routers]] at www.draytek.co.uk (registration required to see article).