If you have been using a local caching-only name server,
you should consider using resolver caching. You can compare the contents
of your local caching-only name server with the contents of the resolver
cache by performing these steps.
Procedure
Perform the following steps to migrate from a local caching-only
name server to resolver caching:
- Display the contents of your caching-only name server and
of the resolver cache at specific intervals.
- For your caching-only name server, you can dump the contents of
the DNS cache. For DNS servers running BIND 9, use the rndc
dumpdb command.
- For the resolver cache, use the Netstat RESCache/-q report. For
more information, see Step for displaying the contents of the cache.
- Compare the contents of the caching-only name server and
the resolver cache, and determine whether to use only resolver caching
or resolver caching with the local caching-only name server, using
the following criteria:
- If the contents are similar, and consist primarily of A, AAAA,
and PTR DNS records, then you would benefit the most by using only
resolver caching. This situation is the most common.
- If the contents are dissimilar, but the caching-only name server
has primarily A, AAAA, and PTR DNS records, then the dissimilar contents
are most likely the result of differences in how the resolver cache
and the caching-only name server delete expired records. In this situation,
you are still most likely to benefit from using only resolver caching.
- If the contents are dissimilar, and the caching-only name server
has many DNS records that are not A, AAAA, or PTR records, you will
probably benefit the most by using both resolver caching and the caching-only
name server. This situation is not common.
- Calculate the amount of resolver cache storage that you
think you need. You can use the default amount of storage
(200 megabytes) or you can use the CACHESIZE resolver setup statement
to specify a maximum amount of storage. For calculation purposes,
1 megabyte of storage holds roughly 400 - 450 cache entries.
- If you are not going to use the local caching-only name
server, stop that server.
Guideline: If the local caching-only name server is the only name
server in the NSINTERADDR list of name servers to be contacted, replace
the caching-only name server entry with one or more name server IP
addresses to be contacted. If there is already more than one name
server in the NSINTERADDR list of name servers, delete the IP address
of the local caching-only name server.