[轉]兩台linux建立GRE隧道

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1.拓撲圖：

備忘：因為應用原因，需要在linux2上添加一個公網地址，並且在中間路由裝置不受控制的情況下，Linux1能訪問到linux2上面的公網地址。

2.基本介面配置：

linux1:192.168.10.1/24

linux2:192.168.20.2/24

R1:

interface FastEthernet0/0
ip address 192.168.10.10 255.255.255.0
no shutdown
!
interface FastEthernet0/1
ip address 192.168.20.10 255.255.255.0
no shutdown

3.路由配置：

linux1網關:192.168.10.10
linux2網關:192.168.20.10
R1：只有直連路由

4.Linux2單網卡多地址配置：

[[email protected] ~]# cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:0
[[email protected] ~]# vi /etc/sysconfig/network-scripts/ifcfg-eth0:0
# Advanced Micro Devices [AMD] 79c970 [PCnet32 LANCE]
DEVICE=eth0:0
BOOTPROTO=none
ONBOOT=yes
HWADDR=00:0c:29:08:48:63
NETMASK=255.255.255.252
IPADDR=202.100.2.2
TYPE=Ethernet
USERCTL=no
IPV6INIT=no
PEERDNS=yes
[[email protected] ~]# service network restart
[[email protected] ~]# ping 202.100.2.2
PING 202.100.2.2 (202.100.2.2) 56(84) bytes of data.
64 bytes from 202.100.2.2: icmp_seq=1 ttl=64 time=0.124 ms
--- 202.100.2.2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.124/0.124/0.124/0.000 ms
[[email protected] ~]# ping 192.168.10.10
PING 192.168.10.10 (192.168.10.10) 56(84) bytes of data.
64 bytes from 192.168.10.10: icmp_seq=1 ttl=255 time=70.6 ms
--- 192.168.10.10 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 70.629/70.629/70.629/0.000 ms

5.GRE tunnel配置：

A.確定是否載入了GRE模組
[[email protected] ~]# lsmod |grep ip_gre
[[email protected] ~]# lsmod |grep ip_gre
B.載入GRE模組

[[email protected] ~]# uname -an
Linux linux1 2.6.9-78.EL #1 Wed Jul 9 15:27:01 EDT 2008 i686 i686 i386 GNU/Linux
[[email protected] ~]# insmod /lib/modules/2.6.9-78.EL/kernel/net/ipv4/ip_gre.ko
[[email protected] ~]# uname -an
Linux linux2 2.6.18-164.el5 #1 SMP Thu Sep 3 03:33:56 EDT 2009 i686 i686 i386 GNU/Linux
[[email protected] ~]# insmod /lib/modules/2.6.18-164.el5/kernel/net/ipv4/ip_gre.ko

C.GRE tunnel介面配置

Linux1:
ip tunnel add tunnel0 mode gre remote 192.168.20.2 local 192.168.10.1 ttl 255
ip link set tunnel0 up mtu 1400
ip addr add 172.16.1.1/30  dev tunnel0
ip addr add 172.16.1.1/30 peer 172.16.1.2/30 dev tunnel0
ip route add 202.100.2.2/32 dev tunnel0
Linux2:
ip tunnel add tunnel0 mode gre remote 192.168.10.1 local 192.168.20.2 ttl 255
ip link set tunnel0 up mtu 1400
ip addr add 172.16.1.2/30  dev tunnel0
ip addr add 172.16.1.2/30 peer 172.16.1.1/30 dev tunnel0
D.將tunnel配置開機運行：

linux1:
vi /etc/init.d/gre.sh   ##內容如下：
insmod /lib/modules/2.6.9-78.EL/kernel/net/ipv4/ip_gre.ko
ip tunnel add tunnel0 mode gre remote 192.168.20.2 local 192.168.10.1 ttl 255
ip link set tunnel0 up mtu 1400
ip addr add 172.16.1.1/30  dev tunnel0
ip addr del 172.16.1.1/30 peer 172.16.1.2/30 dev tunnel0
ip addr add 172.16.1.1/30 peer 172.16.1.2/30 dev tunnel0
ip route add 202.100.2.2/32 dev tunnel0
chmod +x /etc/init.d/gre.sh
echo "/etc/init.d/gre.sh" >> /etc/rc.d/rc.local
linux2:
vi /etc/init.d/gre.sh   ##內容如下：
insmod /lib/modules/2.6.18-164.el5/kernel/net/ipv4/ip_gre.ko
ip tunnel add tunnel0 mode gre remote 192.168.10.1 local 192.168.20.2 ttl 255
ip link set tunnel0 up mtu 1400
ip addr add 172.16.1.2/30  dev tunnel0
ip addr del 172.16.1.2/30 peer 172.16.1.1/30 dev tunnel0
ip addr add 172.16.1.2/30 peer 172.16.1.1/30 dev tunnel0
chmod +x /etc/init.d/gre.sh
echo "/etc/init.d/gre.sh" >> /etc/rc.d/rc.local
D.驗證GRE介面

[[email protected] ~]# ip addr show
1: lo: <LOOPBACK,UP> mtu 16436 qdisc noqueue
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 brd 127.255.255.255 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:0c:29:e4:65:78 brd ff:ff:ff:ff:ff:ff
    inet 192.168.10.1/24 brd 192.168.10.255 scope global eth0
    inet6 fe80::20c:29ff:fee4:6578/64 scope link
       valid_lft forever preferred_lft forever
3: sit0: <NOARP> mtu 1480 qdisc noop
    link/sit 0.0.0.0 brd 0.0.0.0
4: gre0: <NOARP> mtu 1476 qdisc noop
    link/gre 0.0.0.0 brd 0.0.0.0
5: [email protected]: <POINTOPOINT,NOARP,UP> mtu 1400 qdisc noqueue
    link/gre 192.168.10.1 peer 192.168.20.2
    inet 172.16.1.1 peer 172.16.1.2/30 scope global tunnel0
[[email protected] ~]# ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:0c:29:08:48:63 brd ff:ff:ff:ff:ff:ff
    inet 192.168.20.2/24 brd 192.168.20.255 scope global eth0
    inet 202.100.2.2/30 brd 202.100.2.3 scope global eth0:0
    inet6 fe80::20c:29ff:fe08:4863/64 scope link
       valid_lft forever preferred_lft forever
3: sit0: <NOARP> mtu 1480 qdisc noop
    link/sit 0.0.0.0 brd 0.0.0.0
4: gre0: <NOARP> mtu 1476 qdisc noop
    link/gre 0.0.0.0 brd 0.0.0.0
5: [email protected]: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1400 qdisc noqueue
    link/gre 192.168.20.2 peer 192.168.10.1
    inet 172.16.1.2 peer 172.16.1.1/30 scope global tunnel0

5.效果測試：

[[email protected] ~]#  ping 202.100.2.2
PING 202.100.2.2 (202.100.2.2) 56(84) bytes of data.
64 bytes from 202.100.2.2: icmp_seq=0 ttl=64 time=82.4 ms
64 bytes from 202.100.2.2: icmp_seq=1 ttl=64 time=48.7 ms
--- 202.100.2.2 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1002ms
rtt min/avg/max/mdev = 48.784/65.633/82.482/16.849 ms, pipe 2

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