Bug ID 1022997: TCP segments with an incorrect checksum are transmitted when the sock driver is used in AWS deployments (e.g., 1NIC)

Last Modified: Jan 20, 2023

Bug Tracker

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

Known Affected Versions:
14.1.0,,,,,, 14.1.2,,,,,,,,, 14.1.3,, 14.1.4,,,,,,, 14.1.5,,,, 15.1.0,,,,,, 15.1.1, 15.1.2,, 15.1.3,, 15.1.4,, 15.1.5,, 15.1.6,, 15.1.7, 15.1.8,, 16.0.0,, 16.0.1,,, 16.1.0, 16.1.1, 16.1.2,,, 16.1.3,,,

Opened: Jun 03, 2021
Severity: 3-Major


Deployments on AWS that use the sock driver (1NIC, for example) transmit packets with bad checksums when TSO/GSO is required. This causes significant delays as TMM re-segments the packets with correct checksums for retransmission, and may cause some operations to time out (such as configsyncs of large configurations).


-- Delayed packets. -- Possible timeouts for some operations (configsyncs, for example).


-- BIG-IP Virtual Edition (VE) using the sock driver on AWS (all 1NIC deployments use this) -- TSO/GSO required due to MTU limitations on one or more VLANs


Modify (or create, if not present) the file /config/tmm_init.tcl on the affected BIG-IP systems, and add the following line to it: ndal force_sw_tcs off 1d0f:ec20 Then restart TMM: bigstart restart tmm Note: Restarting TMM will cause a failover (or an outage if there is no high availability (HA) peer available).

Fix Information


Behavior Change