Sep 2026 - DevCentral will be set to Read-Only on Sep 14th for a platform update. Details: DevCentral is Evolving.

Forum Discussion

jcbr2002's avatar
jcbr2002
Icon for Nimbostratus rankNimbostratus
Sep 11, 2026

BIG-IP 17.1.2 FastL4 unexpectedly sending TCP RST mid-session

Hi everyone,

 

I am troubleshooting unexpected TCP RST packets physically sent by a BIG-IP 17.1.2 Performance L4 virtual server using the default FastL4 profile.

 

The virtual server performs SNAT and forwards traffic through a single next-hop pool member (the default gateway), so there is no load balancing across multiple servers. There are no traffic policies, iRules, AFM, ASM, or HA/mirroring configured.

 

TCP connections establish successfully, complete TLS, and exchange application data. After that, BIG-IP sends TCP RST packets and terminates the established session. Packet captures suggest that the resets do not appear to be caused by the configured idle timeout.

 

Has anyone seen similar behavior with FastL4 on TMOS 17.1.2, or knows of a configuration, FastL4/TMM behavior, or known issue that could generate RST packets mid-session?

 

Thanks in advance.

1 Reply

  • Additional information: the issue is intermittent and occurs randomly throughout the day. Most connections establish and complete normally, while only some established TLS sessions are unexpectedly reset by BIG-IP after exchanging application traffic. This is not consistently reproducible for every connection.

     

    Thanks in advance.