Dns Configuration; Dns Overview; Static Domain Name Resolution; Dynamic Domain Name Resolution - 3Com 4210 9-Port Configuration Manual

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DNS Configuration

This chapter covers only IPv4 DNS configuration. For details about IPv6 DNS, refer to IPv6
Management Operation.

DNS Overview

Domain name system (DNS) is a mechanism used for TCP/IP applications to provide domain
name-to-IP address translation. With DNS, you can use memorizable and meaningful domain names in
some applications and let the DNS server resolve it into correct IP addresses.
There are two types of DNS services, static and dynamic. Each time the DNS server receives a name
query, it checks its static DNS database before looking up the dynamic DNS database. Reduction of the
searching time in the dynamic DNS database would increase efficiency. Some frequently used
addresses can be put in the static DNS database.

Static Domain Name Resolution

The static domain name resolution means manually setting up mappings between domain names and
IP addresses. IP addresses of the corresponding domain names can be found in the static domain
name resolution table for applications, such as Telnet.

Dynamic Domain Name Resolution

Resolution procedure
Dynamic domain name resolution is implemented by querying the DNS server. The resolution
procedure is as follows:
1) A user program sends a name query to the resolver in the DNS client.
2) The DNS resolver looks up the local domain name cache for a match. If a match is found, it sends
the corresponding IP address back. If not, it sends the query to the DNS server.
3) The DNS server looks up its DNS database for a match. If no match is found, it sends a query to a
higher-level DNS server. This process continues until a result, success or failure, is returned.
4) The DNS client performs the next operation according to the result.
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