1-11 DNS ConfigurationWhen configuring DNS, go to these sections for information you are interested in:z DNS Overviewz Configuring the DNS Clientz Configuring the DNS Proxyz Displaying and Maintaining DNSz DNS Configuration Examplesz Troubleshooting DNS ConfigurationThis document only covers IPv4 DNS configuration. For information about IPv6 DNS configuration,refer to IPv6 Basics Configuration in the IP Services Volume.DNS OverviewDomain Name System (DNS) is a distributed database used by TCP/IP applications to translate domainnames into corresponding IP addresses. With DNS, you can use easy-to-remember domain names insome applications and let the DNS server translate them into correct IP addresses.There are two types of DNS services, static and dynamic. After a user specifies a name, the devicechecks the local static name resolution table for an IP address. If no IP address is available, it contactsthe DNS server for dynamic name resolution, which takes more time than static name resolution.Therefore, some frequently queried name-to-IP address mappings are stored in the local static nameresolution table to improve efficiency.Static Domain Name ResolutionThe static domain name resolution means setting up mappings between domain names and IPaddresses. IP addresses of the corresponding domain names can be found in the static domainresolution table when you use applications such as Telnet.Dynamic Domain Name ResolutionResolving procedureDynamic domain name resolution is implemented by querying the DNS server. The resolutionprocedure is as follows:1) A user program sends a name query to the resolver of the DNS client.2) The DNS resolver looks up the local domain name cache for a match. If a match is found, it sendsthe corresponding IP address back. If not, it sends a query to the DNS server.
