GRE_Server PCA-PCB @chenchih 20160718 

Objective • Teach you how to setup simple Gre-server using two host. This is a simple Gre Server. Connect two host with either public or private ip. We don’t need to install anything. 

Topology 

Basic information • PC(Server)-A – Ip address: 192.168.1.81 – greip: 172.18.1.1 • PC(Server) -B – Ip address: 192.168.140.20 – Greip:172.19.1.1 

Enable gre interface • Enable interface – #sudo modprobe ip_gre • Show interface is it enable – #lsmod |grep gre 

PC-A setting • sudo ip tunnel add gre1 mode gre remote 192.168.140.20 local 192.168.1.81 ttl 255 • sudo ip link set gre1 up • sudo ip addr add 172.18.1.1/24 peer 172.19.1.1/24 dev gre1 • Note: Gre0: is been used, so we have to used gre1 172.18.1.1 =>PC-A gre ip address 172.19.1.2 => PC-B gre ip address 

PC-B setting • sudo ip tunnel add gre1 mode gre remote 192.168.1.81 local 192.168.140.20 ttl 255 • sudo ip link set gre1 up • sudo ip addr add 172.19.1.1/24 peer 172.18.1.1/24 dev gre1 • Note: 172.18.1.1 =>PC-A gre ip address 172.19.1.2 => PC-B gre ip address 

Show route • See route is been establish • ip route show 

ping • Ping A to B, should have gre packet 

Delete interface • Sudo ip link set gre1 down • Sudo ip tunnel del gre1 

reference • http://www.ttlsa.com/linux/create-a-gre- tunnel-linux/ • http://ask.xmodulo.com/create-gre-tunnel- linux.html