Symptoms

When selecting server-side source ports, the BIG-IP system favors ephemeral ports in the upper range.

Impact

If connections on the servers are in the TIME_WAIT state and connection recycling is not configured, the servers may reset those connections that reused a source port too quickly.

Conditions

In many cases, the BIG-IP system needs to select a source port for the server-side flow different than the source port selected by the client. This is always the case when the virtual server's 'source-port' option is set to 'change'.

Workaround

Modify the virtual server's 'source-port' option to 'preserve'. This will reduce the need to find suitable source ports for the server-side by the BIG-IP system.

Fix Information

When searching for an available source port, and wrapping into the privileged port range (<1024), the BIG-IP system now performs a small jump out of that range, thus not going into the upper range unnecessarily.

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips