Bug ID 440620: New connections may be reset when a client reuses the same port as it used for a recently closed connection

Last Modified: Sep 13, 2023

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

Known Affected Versions:
11.6.0, 11.6.1, 11.6.2, 11.6.3,,,,, 11.6.4, 11.6.5, 12.0.0, 12.0.0 HF1, 12.1.0 HF1, 12.0.0 HF2, 12.1.0 HF2, 12.0.0 HF3, 12.0.0 HF4, 12.1.1 HF1, 12.1.1 HF2, 12.1.2 HF1, 12.1.2 HF2, 12.1.0, 12.1.1, 12.1.2, 12.1.3,,,,,, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1, 13.1.0,,,

Fixed In:

Opened: Dec 12, 2013

Severity: 2-Critical


If a client reuses the same port that it used for a recently closed connection, the new connection may receive a RST in response to the client's SYN.


New connections reusing a 4-tuple may be reset for a brief period following a connection close.


A client reuses the same port that it used for a recently closed connection. The 4-tuple of local address, local port, remote address, and remote port must be the same to trigger this issue.


Lowering the "Close Wait" and "Fin Wait 1" timeouts in the TCP profile will shorten the amount of time that a particular 4-tuple remains unusable.

Fix Information

Improved abort handling to better clean up hanging connections.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips