XGS-5240-Series User Manual

Configuration Guide of XGS-5240-Series
69-1
Chapter 69 DNSv4/v6 Configuration
69.1 Introduction to DNS
DNS (Domain Name System) is a distributed database used by TCP/IP applications
to translate domain names into corresponding IPv4/IPv6 addresses. With DNS, you ca
n use easy-to-remember and signification domain names in some applications and let t
he DNS server translate them into correct IPv4/IPv6 addresses.
There are two types of DNS services, static and dynamic, which supplement each
other in application. Each time the DNS server receives a name query it checks its sta
tic DNS database first before looking up the dynamic DNS database. Some frequently
used addresses can be put in the static DNS database, the reduction the searching tim
e in the dynamic DNS database would increase efficiency. The static domain name res
olution means setting up mappings between domain names and IPv4/IPv6 addresses. I
Pv4/IPv6 addresses of the corresponding domain names can be found in the static DN
S database when you use some applications. Dynamic domain name resolution is imple
mented by querying the DNS server. A user program sends a name query to the resol
ver in the DNS client when users want to use some applications with domain name, th
e DNS resolver looks up the local domain name cache for a match. If a match is foun
d, it sends the corresponding IPv4/IPv6 address back to the switch. If no match is foun
d, it sends a query to a higher DNS server. This process continues until a result, whet
her success or failure, is returned.
The Domain Name System (DNS) is a hierarchical naming system for computers, s
ervices, or any resource participating in the Internet. It associates various information wi
th domain names assigned to such participants. Most importantly, it translates humanly
meaningful domain names to the numerical (binary) identifiers associated with networkin
g equipment for the purpose of locating and addressing these devices world-wide. An o
ften used analogy to explain the Domain Name System is that it serves as the "phone
book" for the Internet by translating human-friendly computer hostnames into IP addres
ses.
The Domain Name System makes it possible to assign domain names to groups of
Internet users in a meaningful way, independent of each user's physical location. Beca
use of this, World-Wide Web (WWW) hyperlinks and Internet contact information can re
main consistent and constant even if the current Internet routing arrangements change
or the participant uses a mobile device. Internet domain names are easier to remember
than IP addresses such as 208.77.188.166(IPv4) or 2001:db8:1f70::999:de8:7648:6e8 (I