Bug ID 890229: Source port preserve setting is not honored

Last Modified: May 12, 2022

Affected Product(s):
BIG-IP LTM(all modules)

Known Affected Versions:,,,, 15.1.0,,,,,,,,,,, 13.1.1, 13.1.0

Fixed In:
16.0.0, 15.1.1,,

Opened: Mar 16, 2020

Severity: 3-Major


The source port is always changed in source-port preserve mode even if the original source port with the other parameters would hash to the same TMM.


Applications relying on a specific, fixed source port might not work as expected.


This issue occurs when both of the following conditions are met: -- The virtual server is configured with source-port preserve (the default). -- The system uses one of the following hash configurations including IP addresses. - Using RSS DAG as a default hash on BIG-IP Virtual Edition (VE) (Z100) or on 2000- and 4000-series devices. - Configuring a VLAN's 'CMP Hash' setting to a non-default value. - Using a special variable such as non-default udp.hash or tcp.hash.


Set source-port to preserve-strict.

Fix Information

Now source-port preserve setting does best effort to preserve the source port.

Behavior Change

Beginning with v16.0.0, the TM.PortFind.Src_Preserve db variable introduced in v15.1.0 is no longer supported. The source-port preserve setting now does best effort to preserve the source port.

Guides & references

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