Last Modified: Aug 28, 2026
Affected Product(s):
BIG-IP LTM
Known Affected Versions:
21.1.0
Fixed In:
21.1.0.1
Opened: Jun 12, 2026 Severity: 3-Major
- After upgrading to BIG-IP 21.1.0, pools using certain monitor types such as tcp_half_open monitor may go offline unexpectedly - If a monitor has a recv-disabled string and a particular pool member sends the recv-disabled string, a different pool member may be marked disabled (instead of the correct one) - Pool members show monitor status as down, and /var/log/bigdlog (if bigd debug is enabled) may contain errors such as: get kernel route failed; cannot determine management interface for address [ tmm?=false td=true tr=false addr=::ffff:10.1.1.1:80 srcaddr=::%0:6 ] - No monitor probe traffic is observed for affected pools.
Pools may be marked offline or disabled, causing service disruption or loss of availability for applications relying on those pools
- Upgrade to v21.1.0 - Bigd process using more than one thread To confirm if bigd is running with more than one thread, run the bash command 'ps aux | grep bigd' and check what number is after '-P'. Example output for two threads: root 15966 8735 0.2 0.3 158.0M 52.4M ? S Jun03 00:00:00.83 bigd -P 2
Set bigd to use a single thread by running: # tmsh modify sys db bigd.numprocs value 1 # tmsh save sys config # tmsh restart sys service bigd
None