Bug ID 2209157: FastL4 late binding does not proxy MSS when establishing server-side connection.

Last Modified: Feb 03, 2026

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

Known Affected Versions:
17.1.0, 17.1.0.1, 17.1.0.2, 17.1.0.3, 17.1.1, 17.1.1.1, 17.1.1.2, 17.1.1.3, 17.1.1.4, 17.1.2, 17.1.2.1, 17.1.2.2, 17.1.3, 17.1.3.1, 17.5.0, 17.5.1, 17.5.1.2, 17.5.1.3, 17.5.1.4, 21.0.0, 21.0.0.1

Opened: Jan 22, 2026

Severity: 3-Major

Symptoms

FastL4 late binding does not proxy MSS when establishing server-side connection.

Impact

Sub-optimal connection performance.

Conditions

FastL4 profile with late-binding option enabled.

Workaround

MSS-overwrite option can be used to manually adjust server-side MSS.

Fix Information

None

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips