Bug ID 485472: iRule virtual command allows for protocol mismatch, resulting in crash

Last Modified: Oct 06, 2020

Bug Tracker

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

Known Affected Versions:
11.4.1, 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, 11.5.2, 11.5.2 HF1, 11.6.0, 11.6.0 HF1, 11.6.0 HF2, 11.6.0 HF3, 11.6.0 HF4, 11.6.0 HF5

Fixed In:
12.0.0, 11.6.0 HF6, 11.5.3, 11.4.1 HF9

Opened: Oct 20, 2014
Severity: 3-Major
Related AskF5 Article:


iRule 'virtual' command allows for protocol mismatch.


tmm might crash with assert: 'Must be syncookie'. Traffic is interrupted.


A virtual server with an iRule which leverages the 'virtual' command targeting a virtual server that differs in protocol. For example, a UDP virtual server targeting a TCP virtual server.


This is the result of a misconfiguration. Modify iRules to ensure L4 protocols match between virtual servers.

Fix Information

Resolved issue where TMM might crash with assert: 'Must be syncookie' when the iRule 'virtual' command leads to a protocol mismatch.

Behavior Change