Last Modified: Apr 03, 2026
Affected Product(s):
BIG_IP_NEXT(CNF) CNF
Known Affected Versions:
1.4.0
Opened: Mar 11, 2026 Severity: 3-Major
A pool member monitored by an ICMP health monitor may transition to DOWN even when probe failures are not consecutive. In environments where intermittent packet loss occurs, the monitor may mark the endpoint as down after a single failed probe, even if successful probes occur between them. The default monitor down threshold = 3, the following probe sequence triggers a DOWN state in the following scenario: FAIL ? OK ? FAIL ? OK ? FAIL Instead of requiring three consecutive failures.
Pool members may be marked DOWN prematurely even when the endpoint is still reachable, leading to incorrect pool member health state reporting.
With the default value of monitor down threshold = 3, this issue may occur when: - An ICMP health monitor is configured for a pool member - Probe failures occur intermittently (e.g., due to packet filtering, network instability, or packet loss) - The system counts failed probes cumulatively rather than resetting the counter after successful probes
If the endpoint responds successfully shortly after being marked DOWN, this may indicate that the state change was triggered by intermittent probe failures rather than a persistent service outage. In particular, if the DOWN and subsequent UP events occur at intervals that match the configured monitor probe interval, this behavior may indicate that the endpoint is intermittently failing individual probes rather than experiencing a continuous outage.
None