Caching

You can imagine that with all the machines in the world wanting the IP address of Google that it would severely impact the performance of the root, .com, and Google DNS servers. To combat this, most local DNS servers cache the result of a query for a period of time that is called a TTL (Time to Live). Until this countdown is reached, subsequent DNS lookups for www.google.com will be answered by the local DNS server.

In the rest of this chapter, we discuss configuring a forwarding/caching server, and we also create a small domain to control.

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