Bug ID 490449: LSN translation may occur after an iRule error.

Last Modified: Sep 13, 2023

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

Known Affected Versions:
11.6.0, 11.6.1, 11.6.2, 11.6.3,,,,, 11.6.4, 11.6.5,,,, 12.1.0 HF1, 12.1.0 HF2, 12.1.1 HF1, 12.1.1 HF2, 12.1.2 HF1, 12.1.2 HF2

Fixed In:

Opened: Nov 12, 2014

Severity: 3-Major

Related Article: K13744192


When an iRule throws an error, the default is to abort the connection. When the error occurs in the CLIENT_ACCEPTED event and the Virtual Server is using source-address-translation type LSN, the source address translation may be executed before the connection is aborted. The address translation may succeed even though the connection fails.


There are a number of possible side effects depending on configuration: - Any LSN commands in the failing iRule may be ignored. - LSN Pool translation statistics may be incremented. - A log message indicating a successful translation may be output. - Multiple RSTs may be sent for the aborted connection. - PBA port blocks may be allocated. - Persistence mapping entries may be created. - Inbound mapping entries may be created.


A Virtual Server is using source-address-translation type LSN and has an iRule that does not handle errors.


Use the Tcl catch command to handle Tcl errors. When an error occurs, use the LSN::disable command to prevent the translation.

Fix Information

When an unhandled error occurs in a iRule, the connection will be aborted withoot executing LSN address translation.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips