Networking Fundamentals

Example DNS query

In a lot of cases, the client performs an iterative DNS query, and if the DNS server doesn't know the IP address, it performs a recursive query on behalf of the client. This can be seen in the following diagram:

Figure 13.32: DNS name resolution

The client on the left-hand side wants to communicate with www.packtpub.com, and follows the following process:

1. It checks its own DNS cache but finds no entry.
2. It sends a query to the DNS server specified in the host's configuration.
3. The DNS server checks its own DNS cache but finds no entry. Rather than replying negatively to the host, it undertakes recursive queries.
4. It sends ...