运维必看-GRE隧道配置实践！

从拓扑图能够看到，公司和机房的服务器上各有一个内网IP和外部IP。gre隧道的原理就是把两台服务器的外网IP进行绑定，在两个外网IP直接创建一条隧道tunnel2。tunnel2对服务器看来，就像一个网口，直连着隧道的另外一边。

这里给tunnel配置一个新的IP段：172.16.33.1/2

具体配置

218.188.152.11：

开启路由转发，加载gre协议模块

# echo 1 > /proc/sys/net/ipv4/ip_forward

# modprobe ip_gre

建立隧道tunnel2，添加一虚拟网段172.16.33.0/24

# ip tunnel add tunnel2 mode gre local 218.188.152.11 remote 144.22.1.176 ttl 255 dev eth1

# ip addr add 172.16.33.2 dev tunnel2 peer 172.16.33.1/32

# ip link set dev tunnel2 up

添加一条路由到经过隧道到机房内网的路由

# ip route add 10.65.3.0/24 dev tunnel2

144.22.1.176:

开启路由转发，加载gre协议模块

# echo 1 > /proc/sys/net/ipv4/ip_forward

# modprobe ip_gre

建立隧道tunnel2，添加一虚拟网段172.16.33.0/24

# ip tunnel add tunnel2 mode gre local 144.22.1.176 remote 218.188.152.11 ttl 255 dev em1

# ip addr add 172.16.33.1 dev tunnel2 peer 172.16.33.2/32

# ip link set dev tunnel2 up

添加一条路由到经过隧道到公司内网的路由

# ip route add 192.168.1.0/24 dev tunnel2

查看路由

218.188.152.11：

# netstat -nr

Kernel IP routing table

Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface

172.16.33.1     0.0.0.0         255.255.255.255 UH        0 0          0 tunnel2

192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0

10.65.3.0       0.0.0.0         255.255.255.0   U         0 0          0 tunnel2

0.0.0.0         xx.xx.xx.xx    0.0.0.0         UG        0 0          0 eth0

内网服务器多了172.16.33.1,10.65.3.0/24的两条路由，网关为gre隧道，经过隧道到达机房服务器。

144.22.1.176:

# netstat -nr

Kernel IP routing table

Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface

172.16.33.2     0.0.0.0         255.255.255.255 UH        0 0          0 tunnel2

192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 tunnel2

10.65.3.0       0.0.0.0         255.255.255.0   U         0 0          0 em2

0.0.0.0         xx.xx.xx.xx    0.0.0.0         UG        0 0          0 em1

机房服务器多了172.16.33.2,192.168.1.0/24的两条路由，网关为gre隧道，经过隧道到达机房服务器。

测试网络连通：

218.188.152.11：

# ping 172.16.33.2

PING 172.16.33.2 (172.16.33.2) 56(84) bytes of data.

64 bytes from 172.16.33.2: icmp_seq=1 ttl=64 time=0.048 ms

64 bytes from 172.16.33.2: icmp_seq=2 ttl=64 time=0.059 ms

— 172.16.33.2 ping statistics —

2 packets transmitted, 2 received, 0% packet loss, time 1021ms

rtt min/avg/max/mdev = 0.048/0.053/0.059/0.009 ms

———————————————

# ping 10.65.3.194

PING 10.65.3.194 (10.65.3.194) 56(84) bytes of data.

64 bytes from 10.65.3.194: icmp_seq=1 ttl=64 time=7.96 ms

64 bytes from 10.65.3.194: icmp_seq=2 ttl=64 time=7.63 ms

— 10.65.3.194 ping statistics —

2 packets transmitted, 2 received, 0% packet loss, time 1100ms

rtt min/avg/max/mdev = 7.638/7.799/7.960/0.161 ms

公司服务器能够直接ping通对端机房服务器的gre ip以及内网IP。

144.22.1.176:

# ping 172.16.33.1

PING 172.16.33.1 (172.16.33.1) 56(84) bytes of data.

64 bytes from 172.16.33.1: icmp_seq=1 ttl=64 time=0.018 ms

64 bytes from 172.16.33.1: icmp_seq=2 ttl=64 time=0.016 ms

— 172.16.33.1 ping statistics —

2 packets transmitted, 2 received, 0% packet loss, time 1274ms

rtt min/avg/max/mdev = 0.016/0.017/0.018/0.001 ms

———————————————

# ping 192.168.1.254

PING 192.168.1.254 (192.168.1.254) 56(84) bytes of data.

64 bytes from 192.168.1.254: icmp_seq=1 ttl=64 time=7.81 ms

64 bytes from 192.168.1.254: icmp_seq=2 ttl=64 time=7.97 ms

— 192.168.1.254 ping statistics —

2 packets transmitted, 2 received, 0% packet loss, time 1232ms

rtt min/avg/max/mdev = 7.810/7.894/7.978/0.084 ms

反过来，机房服务器也能够直接ping通对端公司服务器的gre ip以及内网IP。

本文地址：http://www.linuxprobe.com/gre-tunnel-config.html