Ipv4 Dns Configuration; Dns Overview; Static Domain Name Resolution; Dynamic Domain Name Resolution - HP A5120 EI Series Configuration Manual

IPv4 DNS configuration

DNS overview

Domain Name System (DNS) is a distributed database used by TCP/IP applications to translate domain
names into corresponding IP addresses. With DNS, you can use easy-to-remember domain names in
some applications and let the DNS server translate them into correct IP addresses.
DNS services can be static and dynamic. After a user specifies a name, the switch checks the local static
name resolution table for an IP address. If no IP address is available, it contacts the 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 name resolution table to improve
efficiency.

Static domain name resolution

Static domain name resolution means setting up mappings between domain names and IP addresses. IP
addresses of the corresponding domain names can be found in the static domain resolution table when
you use applications such as Telnet.

Dynamic domain name resolution

Resolution process
A user program sends a name query to the resolver of the DNS client.
1.
The DNS resolver looks up the local domain name cache for a match. If the resolver finds a match,
2.
it sends the corresponding IP address back. If not, it sends a query to the DNS server.
The DNS server looks up the corresponding IP address of the domain name in its DNS database. If
3.
no match is found, the server sends a query to a higher level DNS server. This process continues
until a result, whether successful or not, is returned.
After receiving a response from the DNS server, the DNS client returns the resolution result to the
4.
application.
Figure 33 Dynamic domain name resolution
User
program
Request
Resolver
Response
Read Save
Cache
DNS client
Request
Response
DNS server
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