Chapter 1 Dns Configuration; Dns Overview; Static Dns Resolution; Dynamic Dns Resolution - H3C S7500 Series Operation Manual

Operation Manual – DNS
H3C S7500 Series Ethernet Switches

Chapter 1 DNS Configuration

When configuring DNS, go to these sections for information you are interested in:

DNS Overview

Configuring Static Domain Name Resolution
Configuring Dynamic Domain Name Resolution
Displaying and Maintaining DNS Configuration
Troubleshooting DNS Configuration
1.1 DNS Overview
A domain name system (DNS) is a distributed database system that provides domain
name-to-IP address mappings for TCP/IP applications. With DNS, users using IP
applications can directly use meaningful easy-to-remember domain names, which will
be resolved and mapped to corresponding IP addresses by DNS servers.
There are two types of DNS resolution, static and dynamic. When a name query is
received, static resolution is first performed to check the static DNS list. If the static
resolution fails, dynamic resolution is performed to look up the dynamic DNS list.
Because dynamic resolution needs the cooperation of a DNS server and may take
some time, you can put some commonly used domain names into the static DNS list to
improve resolution efficiency.

1.1.1 Static DNS Resolution

With static DNS resolution, you can manually configure some name-to-address
mappings in the static DNS list, and the system will search the static list for
corresponding IP addresses when users use domain names for some applications
(such as telnet).

1.1.2 Dynamic DNS Resolution

I. Resolution procedure
The procedure of dynamic DNS resolution 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 DNS cache for a match. If a match is found, it
returns the corresponding IP address to the user program. If not, it sends a query
request to the DNS server.
3) The DNS server looks up its database for a match. If no match is found, it sends
the request to its parent DNS server. If the parent DNS server does not have the
information, it sends the query to another server. This process continues until a
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Chapter 1 DNS Configuration