domain Dynamic Lookup 三大配置
ip domain name cisco.com
缺省domain-name
ip name-server 131.108.1.111 131.108.1.2
定义DNS SERVER
ip domain lookup
实现DNS 寻址
option dns config
ip name-server 131.108.1.111 131.108.1.2
primary secondary 配置多个DNS SERVER
no ip domain-lookup
no ip domain-lookup [nsap]
当需要配置多个default domain-name时，（default domain-name可以不止一个）
ip domain-list csi.com
ip domain-list telecomprog.edu
ip domain-list merit.edu
DNS spooning (三句)
no ip domain-lookup
ip dns server
使ROUTER作为DNS SERVER
ip dns spooning [acl]
enable使ROUTER对DNS query , request做应答
[acl] 缺省是针对所有主机，可用acl 定义具体主机