Linux 如何建立 GRE 隧道

加载模块

root@livejq:~# lsmod |grep gre
root@livejq:~# modprobe ip_gre
root@livejq:~# lsmod |grep gre
ip_gre                 28672  0
ip_tunnel              24576  1 ip_gre
gre                    16384  1 ip_gre

建立连接

A端
IP:1.1.1.1
Internal Address:10.10.10.1/30

ip tunnel add gredemo mode gre remote 2.2.2.2 local 1.1.1.1
ip link set gredemo up
ip addr add 10.10.10.1/30 dev gredemo

B端
IP:2.2.2.2
Internal Address:10.10.10.2/30

ip tunnel add gredemo mode gre remote 1.1.1.1 local 2.2.2.2 
ip link set gredemo up
ip addr add 10.10.10.2/30 dev gredemo

配置文件（推荐）

这里以 Ubuntu20.04 为例

network:
  ethernets:
    ens160:
      addresses:
      - 1.2.3.4/24
      gateway4: 1.2.3.254
      nameservers:
        addresses:
        - 223.6.6.6
        search: []
    ens192:
      addresses:
      - 192.168.10.8/24
  tunnels:
    gre1:
      mode: gre
      local: 1.2.3.4
      remote: 5.6.7.8
      addresses:
        - 172.17.17.1/30
  version: 2