User's Manual

Configuration Guide of XGS-5240-Series
69-5
ols such as PING, the switch can get corresponding IPv4/IPv6 address with dynamic d
omain name resolution function.
Fig 3-2 DNS SERVER typical environment
The figure above is an application of DNS SERVER. Under some circumstances, t
he client PC doesn’t know the real DNS SERVER, and points to the switch instead. Th
e switch plays the role of a DNS SERVER in two steps: Enable the global DNS SERV
ER function, configure the IP address of the real DNS server. After the DNS SERVER
function is globally enabled, the switch will look up its local cache when receiving a D
NS request from a client PC. If there is a domain needed by the local client, it will dir
ectly answer the client’s request; otherwise, the switch will relay the request to the real
DNS server, pass the reply from the DNS Server to the client and record the domain
and its IP address for a faster lookup in the future.
Switch configuration for DNS CLIENT:
Switch(config)# ip domain-lookup
Switch(config)# dns-server 219.240.250.101
Switch(config)# dns-server 2001::1
Switch#ping host www.sina.com.cn
Switch#traceroute host www.sina.com.cn
Switch#telnet host www.sina.com.cn
Switch configuration for DNS SERVER:
Switch(config)# ip domain-lookup
Switch(config)# dns-server 219.240.250.101
Switch(config)# dns-server 2001::1
Switch(config)# ip dns server
DNS SERVER
IP:219.240.250.101
IPv6:2001::1
INTERNET
SWITCH
client