实验1 配置GRE VPN
实验任务一：GRE VPN基本配置
步骤一：搭建实验环境
在SWA上配置VLAN2，将接口E1/0/2加入VLAN2：
[SWA]vlan 2
[SWA-vlan2]port Ethernet 1/0/2
步骤二：检测公网连通性
查看SWA的路由表和端口状态，确认其工作正常。
[SWA]display ip interface brief
*down: administratively down
(s): spoofing
Interface Physical Protocol IP Address Description Vlan-interface1 up up 1.1.1.2 Vlan-inte...
Vlan-interface2 up up 2.2.2.2 Vlan-inte...
[SWA]display ip routing-table
Routing Tables: Public
Destinations : 6 Routes : 6
Destination/Mask Proto Pre Cost NextHop Interface
1.1.1.0/24 Direct 0 0 1.1.1.2 Vlan1
1.1.1.2/32 Direct 0 0 127.0.0.1 InLoop0
2.2.2.0/24 Direct 0 0 2.2.2.2 Vlan2
2.2.2.2/32 Direct 0 0 127.0.0.1 InLoop0
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0 也可以使用display interface命令。
在RTA和RTB上配置公网接口互通所需的静态路由。
[RTA]interface GigabitEthernet0/0
[RTA-GigabitEthernet0/0]ip address 192.168.1.1 255.255.255.0
[RTA-GigabitEthernet0/0]interface GigabitEthernet0/1
[RTA-GigabitEthernet0/1]ip address 1.1.1.1 255.255.255.0
[RTA-GigabitEthernet0/1]ip route-static 2.2.2.0 255.255.255.0 1.1.1.2
[RTB]interface GigabitEthernet0/0
[RTB-GigabitEthernet0/0]ip address 192.168.2.1 255.255.255.0
[RTB-GigabitEthernet0/0]interface GigabitEthernet0/1
[RTB-GigabitEthernet0/1]ip address 2.2.2.1 255.255.255.0
[RTB-GigabitEthernet0/1]ip route-static 1.1.1.0 255.255.255.0 2.2.2.2 步骤三：配置GRE隧道接口
[RTA] interface Tunnel0
[RTA-Tunnel0] ip address 192.168.3.1 255.255.255.252
[RTA-Tunnel0] source 1.1.1.1
[RTA-Tunnel0] destination 2.2.2.1
[RTB] interface Tunnel0
[RTB-Tunnel0] ip address 192.168.3.2 255.255.255.252
[RTB-Tunnel0] source 2.2.2.1
[RTB-Tunnel0] destination 1.1.1.1
步骤四：为私网配置静态路由
[RTA] ip route-static 192.168.2.0 255.255.255.0 Tunnel0
[RTB] ip route-static 192.168.1.0 255.255.255.0 Tunnel0
配置时也可以用下一跳地址。
步骤五：检验隧道工作状况
查看RTA与RTB的路由表，可见公网、私网路由均存在于路由表中：
[RTB]display ip routing-table
Routing Tables: Public
Destinations : 10 Routes : 10
Destination/Mask Proto Pre Cost NextHop Interface
1.1.1.0/24 Static 60 0
2.2.2.2 GE0/1
2.2.2.0/24 Direct 0 0 2.2.2.1 GE0/1
2.2.2.1/32 Direct 0 0 127.0.0.1 InLoop0
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0
192.168.1.0/24 Static 60 0 192.168.3.2 Tun0
192.168.2.0/24 Direct 0 0 192.168.2.1 GE0/0
192.168.2.1/32 Direct 0 0 127.0.0.1 InLoop0
192.168.3.0/30 Direct 0 0 192.168.3.2 Tun0
192.168.3.2/32 Direct 0 0 127.0.0.1 InLoop0 查看RTA和RTB的隧道接口状态，可见其使用GRE封装，状态为UP：[RTB]display interface Tunnel 0
Tunnel0 current state: UP
Line protocol current state: UP
Description: Tunnel0 Interface
The Maximum Transmit Unit is 1476
Internet Address is 192.168.3.2/30 Primary
Encapsulation is TUNNEL, service-loopback-group ID not set.
Tunnel source 2.2.2.1, destination 1.1.1.1
Tunnel keepalive disable
Tunnel protocol/transport GRE/IP
GRE key disabled
Checksumming of GRE packets disabled
Output queue : (Urgent queuing : Size/Length/Discards) 0/100/0
Output queue : (Protocol queuing : Size/Length/Discards) 0/500/0
Output queue : (FIFO queuing : Size/Length/Discards) 0/75/0
Last 300 seconds input: 15 bytes/sec, 0 packets/sec
Last 300 seconds output: 21 bytes/sec, 0 packets/sec
133 packets input, 5701 bytes
0 input error
124 packets output, 7469 bytes
0 output error
在RTA上打开GRE协议调试开关用debugging命令检验路由器实际收发的报文，说明其地址已经改变。
在PCA上对RTB运行ping命令，但只发送一个ICMP包：
