You can configure a transparent cache on the BIG-IP® system to use external DNS resolvers to resolve queries, and then cache the responses from the resolvers. The next time the system receives a query for a response that exists in the cache, the system immediately returns the response from the cache. The transparent cache contains messages and resource records.
A transparent cache in the BIG-IP system consolidates content that would otherwise be cached across multiple external resolvers. When a consolidated cache is in front of external resolvers (each with their own cache), it can produce a much higher cache hit percentage.
F5 Networks recommends that you configure the BIG-IP system to forward queries, which cannot be answered from the cache, to a pool of local DNS servers rather than the local BIND instance because BIND performance is slower than using multiple external resolvers.
Illustration of BIG-IP system using transparent cache
Perform these tasks to configure a transparent cache on the BIG-IP® system.
You now have an implementation in which the BIG-IP® system caches DNS responses from external DNS resolvers, and answers queries for a cached response. Additionally, the system forwards DNS queries that cannot be answered from the cache to a pool of local DNS servers.