本地局部网地址为192.168.0.0/24,属于保留地址，通过NAT地址翻译功能，局域网用户可以通过ISDN上263网访问Internet。263的ISDN电话号码为95963，用户为263，口令为263，所涉及的命令如下表：
任务
命令
指定接口通过PPP/IPCP地址协商获得IP地址
ip address negotiated
指定内部和外部端口
ip nat {inside | outside}
使用ppp/pap作认证
ppp authentication pap callin
指定接口属于拨号组1
dialer-group 1
定义拨号组1允许所有IP协议
dialer-list 1 protocol ip permit
设定拨号，号码为95963
dialer string 95963
设定登录263的用户名和口令
ppp pap sent-username 263 password 263
设定默认路由
ip route 0.0.0.0 0.0.0.0 bri 0
设定符合访问列表2的所有源地址被翻译为bri 0所拥有的地址
ip nat inside source list 2 interface bri 0 overload
设定访问列表2，允许所有协议
access-list 2 permit any
具体配置如下：
hostname Cisco1720
!
isdn switch-type basic-net3
!
ip subnet-zero
no ip domain-lookup
ip routing
!
interface Ethernet 0
ip address 192.168.0.1 255.255.255.0
ip nat inside
no shutdown
!
interface bri 0
ip address negotiated
ip nat outside
encapsulation ppp
ppp authentication pap callin
ppp multilink
dialer-group 1
dialer hold-queue 10
dialer string 95963
dialer idle-timeout 120
ppp pap sent-username 263 password 263
no cdp enable
no ip split-horizon
no shutdown
!
ip classless
!
! Static Routes
!
ip route 0.0.0.0 0.0.0.0 bri 0
!
! Access Control List 2
!
access-list 2 permit any
!
dialer-list 1 protocol ip permit
!
! Dynamic NAT
!
ip nat inside source list 2 interface bri 0 overload
snmp-server community public ro
!
line console 0
exec-timeout 0 0
!
line vty 0 4
!
end
