Last Modified: Oct 22, 2026
Affected Product(s):
BIG-IP DNS
Known Affected Versions:
17.1.3.6, 17.5.1.10, 21.1.0.3
Opened: Oct 16, 2026 Severity: 4-Minor
When a DNS cache resolver has a very large number of cached resource records (in the order of millions) and the last Virtual Server referencing the cache is deleted, the tmm process might take a long time to remove the cache and free its memory, might miss its heartbeat signal and might be restarted. See https://my.f5.com/manage/s/article/K9231 for more details on tmm and its heartbeat timeout.
The TMM process is prevented from servicing its heartbeat and can be restarted
- DNS module provisioned - DNS cache resolver configured on a DNS profile and in use - The DNS cache resolver contains a large number of cached resource records (in the order of millions) - The last Virtual Server referencing the DNS profile and the DNS cache resolver is deleted
Before deleting the last Virtual Server referencing a DNS cache, wait until most of the Resource Records present in the cache have expired. The number of resource records in the cache can be monitored with this command: "tmsh show ltm dns cache records rrset cache <CACHE_NAME> count-only" Check K42437613 for more details
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