Bug ID 483157: Server-side flow uses 0 as TCP source port

Last Modified: Oct 06, 2020

Bug Tracker

Affected Product:  See more info
BIG-IP LTM(all modules)

Known Affected Versions:
11.5.0, 11.5.1, 11.5.1 HF1, 11.5.1 HF10, 11.5.1 HF11, 11.5.1 HF2, 11.5.1 HF3, 11.5.1 HF4, 11.5.1 HF5, 11.5.1 HF6, 11.5.1 HF7, 11.5.1 HF8, 11.5.1 HF9, 11.5.10

Fixed In:

Opened: Oct 07, 2014
Severity: 3-Major
Related AskF5 Article:


The BIG-IP system might use 0 (zero) as the TCP source port for server-side flows.


Many network stacks use 0 as reserved port and do not treat the value as valid for TCP source ports. This might cause TCP ports to be reused too quickly.


This occurs when the server-side VLAN's cmp_hash is either src-ip or dst-ip (the default value is 'default') and the server-side source_port mode is set to change.



Fix Information

The BIG-IP system no longer uses 0 (zero) as the TCP source port for server-side flows, so TCP ports are not reused too quickly.

Behavior Change