Setting up GRE Tunnels on Debian ๐


To set up a GRE tunnel on Debian between two endpoints (102.219.109.8
and 102.222.161.20
) using tunnel IPs 100.64.0.1/30
and 100.64.0.2/30
, follow these steps.
โ Step-by-Step GRE Tunnel Setup on Debian
๐ฅ๏ธ Assumptions:
Host | Public IP | Tunnel IP |
Host A | 102.219.109.8 | 100.64.0.1/30 |
Host B | 102.222.161.20 | 100.64.0.2/30 |
Youโll need to do the following steps on both hosts, changing local/remote accordingly.
๐ง 1. Create the GRE tunnel
On Host A (102.219.109.8
)
ip tunnel add gre1 mode gre local 102.219.109.8 remote 102.222.161.20 ttl 255
ip addr add 100.64.0.1/30 dev gre1
ip link set gre1 up
On Host B (102.222.161.20
)
ip tunnel add gre1 mode gre local 102.222.161.20 remote 102.219.109.8 ttl 255
ip addr add 100.64.0.2/30 dev gre1
ip link set gre1 up
๐ 2. Test the Tunnel
From Host A, ping Host B:
ping 100.64.0.2
From Host B, ping Host A:
ping 100.64.0.1
๐พ 3. Make it Persistent (Optional)
If you want to make the tunnel persistent across reboots, you can:
Option A: Use a systemd unit or init script
(not ideal unless scripted manually)
Option B: Use /etc/network/interfaces
(legacy method)
Edit /etc/network/interfaces
on Host A:
auto gre1
iface gre1 inet static
address 100.64.0.1
netmask 255.255.255.252
pre-up ip tunnel add gre1 mode gre local 102.219.109.8 remote 102.222.161.20 ttl 255
up ip link set gre1 up
down ip link set gre1 down
post-down ip tunnel del gre1
Edit /etc/network/interfaces
on Host B:
auto gre1
iface gre1 inet static
address 100.64.0.2
netmask 255.255.255.252
pre-up ip tunnel add gre1 mode gre local 102.222.161.20 remote 102.219.109.8 ttl 255
up ip link set gre1 up
down ip link set gre1 down
post-down ip tunnel del gre1
Then restart networking:
sudo systemctl restart networking
๐ Notes
Ensure GRE (IP protocol 47) is allowed through any firewall (iptables, nftables, cloud firewall, etc.).
No NAT should be applied to the tunnel unless explicitly required.
GRE doesn't encrypt traffic โ it's purely encapsulation.
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Ronald Bartels
Ronald Bartels
Driving SD-WAN Adoption in South Africa