Caching-Only Servers
Creating caching-only name servers is another alternative when you need more servers. Caching-only name servers are name servers not authoritative for any zones (except for the automatically created reverse-mapping zones). The name doesn’t imply that primary master and secondary name servers don’t cache—they do—but rather that the only function this server performs is looking up data and caching it. As with primary master and secondary name servers, a caching-only name server needs a cache.dns file and the automatically created zones, 0.in-addr.arpa, 127.in-addr.arpa, and 255.in-addr.arpa. The configuration of a caching-only server looks like Figure 9-4.
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A caching-only name server can look up domain names inside and outside your zone, as can primary master and secondary name servers. The difference is that when a caching-only name server initially looks up a name within your zone, it ends up asking one of your zone’s primary master or secondary name servers for the answer. A primary or secondary would answer the same question out of its authoritative data. Which primary or secondary does the caching-only server ask? As with name servers outside of your domain, it finds out which name servers serve your zone from one of the name servers for your parent zone. Is there any way to prime a caching-only ...
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