Bug ID 2135621: Poor TCP performance on Hyper-V non-accelerated deployments with Cisco VIC interfaces

Last Modified: Nov 25, 2025

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

Known Affected Versions:
17.5.1, 17.5.1.2, 17.5.1.3, 21.0.0

Opened: Oct 17, 2025

Severity: 3-Major

Symptoms

TCP retransmits occur on Hyper-V deployments with Cisco VIC networks (SR-IOV disabled). The problem is related to large segments processing (TSO packets)

Impact

Poor TCP performance for virtual servers with TCP profile

Conditions

- Hyper-V VM with Network adapter on top of Cisco VIC interface - SR-IOV is not enabled - Virtual server uses TCP profile

Workaround

- Disable TSO feature: tmsh modify sys db tm.tcpsegmentationoffload value disable - Other workaround is to switch to sock driver: https://my.f5.com/manage/s/article/K000153024

Fix Information

None

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips