Repeater linking

I am testing network configurations for TARRA, the Teton Amateur Radio Repeater Association in Wyoming.

Goal here is to route our 44 subnet to the repeaters. The repeaters can be on any service provider so we need to accommodate that.

I have to keep in mind that the bigger picture is to control and link the repeaters, so that might mean changing out the operating system. For example, the Pi image distributed for Allstar is ArchLinux.

Wireguard would be one approach but my current thought is to keep it as simple as possible by using only tunnels.

Test setup

I am using a Pi4 and a Pi3 for testing right now, using the official image based on Debian.

Violet is the pi3, connected over Wifi so I can ssh into it

Tenrec is the pi4, connected by a 10BT patch cable to violet. Tenrec has a 7" screen and kbd.

Tools you will be be needing.

apt install tcpdump

Tunnels

GRE tunnels

Basics

• https://david-waiting.medium.com/a-beginners-guide-to-generic-routing-encapsulation-fb2b4fb63abb
• https://www.xmodulo.com/create-gre-tunnel-linux.html

Types and basic commands

On Raspbian I had to create a file to load the modules at boot, in this order.

cd /etc/modules-load.d
cat > tunnel.conf
gre
ip_tunnel
ip_gre

I reboot at this point and make sure the modules are loading, with

lsmod | grep gre

TUN interface - encapsulates ether header

The "gre0" interface exists so if I try to use the first command with gre0 I get an 'exists' error, I could follow the first example above and use "tun0" instead of "gre0"?

On violet,

ip tunnel add tun0 mode gre remote 172.16.123.1 local 172.16.123.2 ttl 255
ip addr add 10.10.10.1/24 dev tun0
ip link set tun0 up

On tenrec, the other way round,

ip tunnel add tun0 mode gre remote 172.16.123.2 local 172.16.123.1 ttl 255
ip addr add 10.10.10.2/24 dev tun0
ip link set tun0 up

To shutdown simply use, then press on and test TAP.

ip link set tun0 down

TAP interface - no ether header

On violet,

ip link add tun1 type gretap remote 172.16.123.1 local 172.16.123.2 dev eth0
ip addr add 10.10.10.1/24 dev tun1
ip link set tun1 up
ip -d link show tun1

On tenrec, going the other direction,

ip link add tun1 type gretap remote 172.16.123.2 local 172.16.123.1 dev eth0
ip addr add 10.10.10.2/24 dev tun1
ip link set tun1 up
ip -d link show tun1

I need some sample commands here to confirm the links actually work.

ping 10.10.10.1
ping 172.16.123.1

tcpdump -i tun0

Wireguard

Wireguard is an encrypted tunnel that is easy to set up.

Instructions and download are available from https://github.com/WireGuard/wireguard-vyatta-ubnt/wiki/EdgeOS-and-Unifi-Gateway