linux gre隧道创建
实验环境
两台可以相互通信的虚拟机，两个虚拟机在不通的网段。如下所示
host A:
[root@10-10-10-47 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1454 qdisc pfifo_fast state UP group default qlen 1000
link/ether 52:54:00:f6:21:28 brd ff:ff:ff:ff:ff:ff
inet 10.10.10.47/24 brd 10.10.10.255 scope global eth0
valid_lft forever preferred_lft foreverhost B:
[root@192-168-0-118 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1454 qdisc pfifo_fast state UP group default qlen 1000
link/ether 52:54:00:14:91:76 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.118/24 brd 192.168.0.255 scope global eth0
valid_lft forever preferred_lft forever两台虚拟机之间可以相互通信
[root@192-168-0-118 ~]# ping 10.10.10.47
PING 10.10.10.47 (10.10.10.47) 56(84) bytes of data.
64 bytes from 10.10.10.47: icmp_seq=1 ttl=63 time=1.04 ms
64 bytes from 10.10.10.47: icmp_seq=2 ttl=63 time=0.440 ms
64 bytes from 10.10.10.47: icmp_seq=3 ttl=63 time=0.368 ms
64 bytes from 10.10.10.47: icmp_seq=4 ttl=63 time=0.561 ms
^C
--- 10.10.10.47 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3001ms
rtt min/avg/max/mdev = 0.368/0.602/1.040/0.262 ms实验目的
在host A和host B之间建里gre隧道，另外在机器A 上面配置 2.2.2.2， 在机器B上面配置1.1.1.1 ，然后在A上面能够ping -I 2.2.2.2 1.1.1.1 能够通。
实验步骤
1、在host A（10.10.10.47）上面操作
ip tunnel add gre-test mode gre remote 192.168.0.118 local 10.10.10.47 ttl 255
ip link set gre-test up
ip route add 1.1.1.1/32 dev gre-test
ip addr add 2.2.2.2 dev gre-test
ip link set gre-test down操作过程入下图
[root@10-10-10-47 ~]# ip tunnel add gre-test mode gre remote 192.168.0.118 local 10.10.10.47 ttl 255
[root@10-10-10-47 ~]# ip link set gre-test up
[root@10-10-10-47 ~]# ip route add 1.1.1.1/32 dev gre-test
[root@10-10-10-47 ~]# ip addr add 2.2.2.2 dev gre-test
[root@10-10-10-47 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1454 qdisc pfifo_fast state UP group default qlen 1000
link/ether 52:54:00:f6:21:28 brd ff:ff:ff:ff:ff:ff
inet 10.10.10.47/24 brd 10.10.10.255 scope global eth0
valid_lft forever preferred_lft forever
3: gre0@NONE: <NOARP> mtu 1476 qdisc noop state DOWN group default qlen 1000
link/gre 0.0.0.0 brd 0.0.0.0
4: gretap0@NONE: <BROADCAST,MULTICAST> mtu 1462 qdisc noop state DOWN group default qlen 1000
link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
5: gre-test@NONE: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1430 qdisc noqueue state UNKNOWN group default qlen 1000
link/gre 10.10.10.47 peer 192.168.0.118
inet 2.2.2.2/32 scope global gre-test
valid_lft forever preferred_lft forever
[root@10-10-10-47 ~]# ip r
default via 10.10.10.1 dev eth0
1.1.1.1 dev gre-test scope link
10.10.10.0/24 dev eth0 proto kernel scope link src 10.10.10.472、在host B（192.168.0.118）上面操作
ip tunnel add gre-test mode gre remote 10.10.10.47 local 192.168.0.118 ttl 255
ip link set gre-test up
ip route add 2.2.2.2/32 dev gre-test
ip addr add 1.1.1.1 dev gre-test
ip link set gre-test down
[root@192-168-0-118 ~]# ip tunnel add gre-test mode gre remote 10.10.10.47 local 192.168.0.118 ttl 255
[root@192-168-0-118 ~]# ip link set gre-test up
[root@192-168-0-118 ~]# ip route add 2.2.2.2/32 dev gre-test
[root@192-168-0-118 ~]# ip addr add 1.1.1.1 dev gre-test
[root@192-168-0-118 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1454 qdisc pfifo_fast state UP group default qlen 1000
link/ether 52:54:00:14:91:76 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.118/24 brd 192.168.0.255 scope global eth0
valid_lft forever preferred_lft forever
3: gre0@NONE: <NOARP> mtu 1476 qdisc noop state DOWN group default qlen 1000
link/gre 0.0.0.0 brd 0.0.0.0
4: gretap0@NONE: <BROADCAST,MULTICAST> mtu 1462 qdisc noop state DOWN group default qlen 1000
link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
6: gre-test@NONE: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1430 qdisc noqueue state UNKNOWN group default qlen 1000
link/gre 192.168.0.118 peer 10.10.10.47
inet 1.1.1.1/32 scope global gre-test
valid_lft forever preferred_lft forever
[root@192-168-0-118 ~]# ip r
default via 192.168.0.1 dev eth0
2.2.2.2 dev gre-test scope link
192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.118实验结果
[root@10-10-10-47 ~]# ping -I 2.2.2.2 1.1.1.1 -c 4
PING 1.1.1.1 (1.1.1.1) from 2.2.2.2 : 56(84) bytes of data.
64 bytes from 1.1.1.1: icmp_seq=1 ttl=64 time=0.635 ms
64 bytes from 1.1.1.1: icmp_seq=2 ttl=64 time=0.702 ms
64 bytes from 1.1.1.1: icmp_seq=3 ttl=64 time=0.588 ms
64 bytes from 1.1.1.1: icmp_seq=4 ttl=64 time=0.565 ms
--- 1.1.1.1 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3000ms
rtt min/avg/max/mdev = 0.565/0.622/0.702/0.058 ms还原实验环境
在host A（10.10.10.47）执行
ip link set gre-test down
ip tunnel del gre-test
[root@10-10-10-47 ~]# ip link set gre-test down
[root@10-10-10-47 ~]# ip tunnel del gre-test
[root@10-10-10-47 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1454 qdisc pfifo_fast state UP group default qlen 1000
link/ether 52:54:00:f6:21:28 brd ff:ff:ff:ff:ff:ff
inet 10.10.10.47/24 brd 10.10.10.255 scope global eth0
valid_lft forever preferred_lft forever
3: gre0@NONE: <NOARP> mtu 1476 qdisc noop state DOWN group default qlen 1000
link/gre 0.0.0.0 brd 0.0.0.0
4: gretap0@NONE: <BROADCAST,MULTICAST> mtu 1462 qdisc noop state DOWN group default qlen 1000
link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff在host B（192.168.0.118）执行
ip link set gre-test down
ip tunnel del gre-test
[root@192-168-0-118 ~]# ip link set gre-test down
[root@192-168-0-118 ~]# ip tunnel del gre-test
[root@192-168-0-118 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1454 qdisc pfifo_fast state UP group default qlen 1000
link/ether 52:54:00:14:91:76 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.118/24 brd 192.168.0.255 scope global eth0
valid_lft forever preferred_lft forever
3: gre0@NONE: <NOARP> mtu 1476 qdisc noop state DOWN group default qlen 1000
link/gre 0.0.0.0 brd 0.0.0.0
4: gretap0@NONE: <BROADCAST,MULTICAST> mtu 1462 qdisc noop state DOWN group default qlen 1000
link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff最后还有一个gre0，不能用
ip link set gre0 down
ip tunnel del gre0
上面两个命令删除，否则会报错
[root@10-10-10-47 ~]# ip link set gre0 down
[root@10-10-10-47 ~]# ip tunnel del gre0
delete tunnel “gre0” failed: Operation not permitted
需要按照下面的命令删除：
[root@192-168-0-118 ~]# lsmod|grep gre
ip_gre 22931 0
gre 13144 1 ip_gre
ip_tunnel 25163 1 ip_gre
[root@192-168-0-118 ~]# rmmod ip_gre
[root@192-168-0-118 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1454 qdisc pfifo_fast state UP group default qlen 1000
link/ether 52:54:00:14:91:76 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.118/24 brd 192.168.0.255 scope global eth0
valid_lft forever preferred_lft forever
[root@192-168-0-118 ~]# 整个实验过程比较简单，自己操作一遍才能把这些基本的命令熟悉起来。