Table of Contents
Assumptions #
You are running Ubuntu 18.04 or 20.04 without netplan (netplan is a new version)
Requirements: 10 minutes of your time, root SSH access, and knowledge of text editor on
system (eg, vim or nano).
Guide:
- SSH into your machine and elevate to root by executing the following: sudo bash
- Once you are elevated, execute the following: cd /etc/networking/
- Once here, use your choice of text editor (vim or nano) to edit the interfaces file
- Add the following content to the /etc/networking/interfaces file:
auto symmetrical
iface symmetrical inet tunnel
address 10.10.56.2 # REPLACE
netmask 255.255.255.252
mode gre
mtu 1440
endpoint 205.220.230.49 # REPLACE
local 1.1.1.1 # REPLACE WITH YOUR LOCAL IP
ttl 255
post-up ip route add default via 10.10.56.1 table symmetricaltunnel
post-ip ip rule add from YOURIP/CIDR table symmetricaltunnel # eg: ip rule add
from 172.111.1.0/24 table symmetricaltunnel
post-up ip addr add YOURIP/CIDR dev symmetrical # eg: ip addr add
172.111.1.1/24 dev symmetrical
pre-down ip rule del from YOURIP/CIDR table symmetricaltunnel
pre-down ip route del default via 10.10.56.1 table symmetricaltunnel - Substitute the assumed variables (eg,
10.10.56.1,10.10.56.2,205.220.230.49,1.1.1.1,YOURIP/CIDR) with the expected
values - Save and quit the file (in vim: ESC :wq or nano: ctrl+x)
- Add the routing table (ONLY DO THIS ONCE) to the system by executing the
following:
echo ‘net.ipv4.ip_forward=1′ >> /etc/sysctl.conf && sysctl -p && echo ‘500 PATH’ >>
/etc/iproute2/rt_tables - Then you should be able to execute the following command:
ip link set dev symmetrical up - Then you should be able to ping the other end of the tunnel if your changes worked
successfully:
ping 10.10.56.1 # SUBSTITUTE PROPER IP HERE - Woohoo! That’s how the cookie crumbles.
auto lectron
iface lectron inet tunnel
address 10.10.56.1 (local-ip-address-assigned-to-you)
netmask 255.255.255.252 (because your private subnet is /30 which equals to the .252 suffix)
mode gre
mtu 1440
endpoint 205.220.230.49
local (your-server-ip-address)
ttl 255
post-up ip route add 0.0.0.0/0 via 10.10.56.2 table 123
post-up ip rule add from 168.100.15.0/32 table 123
post-up ip address add 168.100.15.0/32 dev lectron
pre-down ip route del 0.0.0.0/0 via 10.10.56.2 table 123
pre-down ip rule del from 168.100.15.0/32 table 123