Bug ID 446540: DNS Cache - Size Issue

Last Modified: Apr 10, 2019

Bug Tracker

Affected Product:  See more info
BIG-IP LTM(all modules)

Known Affected Versions:
11.2.1, 11.3.0, 11.4.0, 11.4.1, 11.5.0

Fixed In:
11.6.0, 11.5.1, 11.5.0 HF1, 11.4.1 HF4

Opened: Jan 28, 2014
Severity: 3-Major
Related AskF5 Article:


TMM with a DNS Virtual server and attached DNS Cache cores with a specific backtrace.


TMM will restart and traffic flow will be disrupted.


A DNS cache is configured with one or more very large sub-caches (RRset, msg, nameserver, key).


Lower DNS sub-cache (RRset, msg, key) sizes to 150mb or less (nameserver should be < 1 million entries), that is do not over-provision memory available on BIGIP.

Fix Information

TMM will no longer core/restart with this backtrace due to large DNS sub-cache sizes. Please note that it is still advised to restrict cache size to fit within available memory. Be conservative and size up given available memory. Note for EACH configured cache, the sum of the sub-cache sizes (rrset + msg + nameserver + key), times the number of TMM threads, is approximately the size the cache may occupy in memory (it will actually occupy slightly more). Each configured cache consumes its own amount of memory -- configured caches do not share memory. Their sum must not exceed available memory of TMM. Note also TMM does not have control over all available system memory -- some is left available for the host; this is platform dependent.

Behavior Change