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动态地址Site-to-Site VPN

    利用Internet 出口线路建立VPN通道实现总、分公司之间的互联,是目前许多公司热衷的方案。以往要建立这样的VPN,需要至少一端使用静态的IP地址。当前很多公司都通过ADSL方式上网,如果要求电信提供静态地址,费用将会大大增加(如深圳512K固定IP的ADSL月租是RMB5000)。现在Cisco IOS 12.3(4)T中新增了根据DNS名称来建立VPN peer 的命令,借助希网(3322.org)、88ip等动态域名解释系统的配合,可以在VPN两端都使用动态地址的ADSL线路,节省大笔费用。
  
  关键命令:
  set peer {host-name [dynamic] | ip-address}
  说明:
  host-name 指定IPSec peer的DNS主机名称,如:myhost.example.com。
  dynamic (可选参数) 指定 IPSec peer 的主机名在需要建立IPSec通道的时候才通过DNS服务器解释为IP地址。
  ip-address 直接给出IPSec peer的IP地址(传统的配置方式)。
  
  示例拓扑图:
  
  
  为简单起见实验中使用的是静态地址,实际环境中局域网内应在一台机器上运行动态域名解释客户端程序,以将主机名nbo.3322.org注册到服务器,注册地址是路由器的外网端口地址。
  
  配置:
  VPN-1(省略了部分无关配置):
  
  version 12.3
  !
  hostname vpn-1
  !
  aaa new-model
  !
  aaa authentication login authen group radius local
  aaa authorization network author local
  aaa session-id common
  ip subnet-zero
  !
  ip cef
  ip name-server 202.96.134.133
  !
  crypto isakmp policy 10
  authentication pre-share
  group 2
  crypto isakmp key cisco address 0.0.0.0 0.0.0.0
  !
  crypto ipsec transform-set s2s esp-des esp-sha-hmac
  !
  crypto dynamic-map dymap 1
  set transform-set s2s
  match address 110
  !
  crypto map mymap 1 ipsec-isakmp dynamic dymap
  !
  interface FastEthernet0/0
  description VPN
  ip address 202.11.22.11 255.255.255.248
  ip nat outside
  crypto map mymap
  !
  interface FastEthernet0/1
  description INSIDE_GATEWAY
  ip address 172.16.10.110 255.255.0.0
  ip nat inside
  !
  ip nat inside source route-map nonat interface FastEthernet0/0 overload
  ip classless
  ip route 0.0.0.0 0.0.0.0 FastEthernet0/0
  no ip http server
  !
  access-list 110 permit ip 172.16.0.0 0.0.255.255 172.30.1.0 0.0.0.255
  access-list 120 deny  ip 172.16.0.0 0.0.255.255 172.30.1.0 0.0.0.255
  access-list 120 permit ip 172.16.0.0 0.0.255.255 any
  route-map nonat permit 10
  match ip address 120
  !
  end
  
  VPN-2(省略了部分无关配置):
  
  version 12.3
  !
  hostname vpn-2
  !
  username mize password 0 http://mize.netbuddy.org
  no aaa new-model
  ip subnet-zero
  !
  ip cef
  ip name-server 202.96.134.133
  !
  crypto isakmp policy 1
  authentication pre-share
  group 2
  crypto isakmp key cisco hostname nbo.3322.org
  !
  crypto ipsec transform-set s2s esp-des esp-sha-hmac
  !
  crypto map mymap 10 ipsec-isakmp
  set peer nbo.3322.org dynamic
  set transform-set s2s
  match address 110
  !
  interface FastEthernet0/0
  ip address 202.11.22.43 255.255.255.248
  ip nat outside
  crypto map mymap
  !
  interface FastEthernet0/1
  ip address 172.30.1.1 255.255.255.0
  ip nat inside
  !
  ip nat inside source route-map nonat interface FastEthernet0/0 overload
  ip classless
  ip route 0.0.0.0 0.0.0.0 FastEthernet0/0
  !
  access-list 110 permit ip 172.30.1.0 0.0.0.255 172.16.0.0 0.0.255.255
  access-list 120 deny  ip 172.30.1.0 0.0.0.255 172.16.0.0 0.0.255.255
  access-list 120 permit ip 172.30.1.0 0.0.0.255 any
  route-map nonat permit 10
  match ip address 120
  !
  end
  
  相关调试命令:
  show cry isa sa
  show cry ipsec sa (责任编辑:IT)