Bug ID 741203: DNS cache will respond from cache for records with TTL=0

Last Modified: Jul 03, 2019

Bug Tracker

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

Known Affected Versions:
12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2, 12.1.2, 12.1.2 HF1, 12.1.2 HF2, 12.1.3, 12.1.3.1, 12.1.3.2, 12.1.3.3, 12.1.3.4, 12.1.3.5, 12.1.3.6, 12.1.3.7, 12.1.4, 12.1.4.1, 14.1.0, 14.1.0.1, 14.1.0.2, 14.1.0.3, 14.1.0.4, 14.1.0.5, 14.1.0.6, 15.0.0

Opened: Aug 20, 2018
Severity: 4-Minor

Symptoms

When a query reply with TTL=0 is received by DNS cache, the BIG-IP system caches the result for a short amount of time (slightly less than one second). Queries made to the cache during this time receive a response from the cache, and do not come from the origin server.

Impact

Even though the TTL of zero implies that responses are not cached, they are. This means that for clients requesting that cached record during that very short period of time (less than a second) the BIG-IP system sends it from the cache, rather than from the origin DNS server.

Conditions

-- DNS cache is configured. -- A query reply with TTL=0 is received by DNS cache

Workaround

None.

Fix Information

None

Behavior Change