Kemp Support, how can we help?

The latest application delivery knowledge and expertise at your fingertips.

Changes Affecting Long-Lived UDP Connections

This article relates to LoadMaster firmware version 7.2.53.

It is common for some applications (such as Citrix Virtual Desktop Infrastructure and Microsoft Always On VPN) to open UDP connections that last days or even weeks. To address persistence and port following issues seen for these long-lived UDP connections, the following changes have been made to Layer 7 Virtual Services in LoadMaster firmware version 7.2.53.

Increased Maximum Persistence Timeout

The maximum value of the persistence timeout setting has increased from 7 days to 28 days. You can configure the persistence Timeout drop-down list when a persistence Mode is selected in the Standard Options section of the Virtual Service modify screen (Virtual Services > View/Modify Services > Modify).

Persistence Refresh

If the persistence Timeout is set to 4 days or more, a Refresh Persist check box appears. This is disabled by default. When Refresh Persist is enabled, the persist entries are auto-refreshed each day for long-lived connections.

RESTful Application Programming Interface (API) Details

To configure the persisttimeout value, run the modvs command. For example:


The persisttimeout value is specified in seconds. So, the example above (2419200) sets the persist timeout to 28 days.

To enable or disable the refreshpersist value, run the modvs command. For example:


Valid values for the refreshpersist parameters are as follows:

  • 0 - Disabled

  • 1 - Enabled

For further details on the RESTful API in general, refer to the Long Term Support (LTS) RESTful API Interface Description document.