Last Modified: Apr 28, 2025
Affected Product(s):
BIG-IP LTM
Known Affected Versions:
13.0.0
Fixed In:
13.1.0, 13.0.1, 12.1.3, 11.6.3, 11.5.5
Opened: Apr 12, 2017 Severity: 3-Major Related Article:
K20228504
In some cases, an active BIG-IP may fail to forward the SYN on the server-side when handling traffic for a mirrored FastL4 virtual after receiving a context ACK from the standby BIG-IP. Symptoms include: -- TCP connection failures. -- Possibly other packets lost.
FastL4 mirroring does not always forward SYN to server after receiving context ACK. Connections fail.
-- FastL4 virtual server. -- Mirroring is enabled. -- Certain traffic interleaving might be necessary for this intermittent problem to occur.
Set the tm.fastl4_ack_mirror db variable using the following command: tmsh modify sys db tm.fastl4_ack_mirror value disable
In this release, mirrored FastL4 virtual servers now forward the SYN on the server-side after receiving the context-ack from the peer as expected.