Bug ID 513436: Setting source-port to preserve-strict in HW guaranteed mode

Last Modified: Jul 13, 2024

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

Known Affected Versions:
12.0.0, 12.0.0 HF1, 12.0.0 HF2, 12.0.0 HF3, 12.0.0 HF4

Opened: Mar 19, 2015

Severity: 2-Critical


Setting the virtual server option 'source-port' to 'preserve-strict' causes client-side and server-side flows to hash to different TMMs.


This results in server-side flows being fast forwarded, and in hardware acceleration guaranteed mode, the TMM fast forwarded flows will be reset causing a small percentage of client connections to be disconnected prematurely.


This occurs when the following conditions are met: -- A virtual server is configured with a FastL4 profile using 'guaranteed' hardware acceleration (ePVA). -- The virtual server 'source-port' is set to 'preserve-strict'.


Although this is intended functionality, setting virtual server 'source-port' to 'preserve' or less allows the TMM to source from a port hashing to the same TMM as the client-side.

Fix Information


Behavior Change

Guides & references

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