Because in the [last post](https://deavmi.assigned.network/blog/ipv6_over_babel_part1/) we did it and now I want to continue working on it.
# What?
In part 1 we got setup with two RNode's running in their TNC (terminal node controller) mode. We were able to turn these into virtual networking interfaces that would appear on both $node_A$ and $node_b$ as `tnc0`.
## A new topology
What we now want to do is to introduce a third node, $node_c$, which will be placed into the following topology:
What we want to setup this time is the following:
1. Every node from $node_a \space ...\space node_c$ should be running an identical Babe configuration as we showed last time
2. $node_a$ must be in radio range of $node_c$
3. $node_b$ must be in radio range of $node_c$
4. There should be **no** radio overlap between $node_a$ and $node_b$. We don't want overlap as we want to force traffic from $node_a$ to travel _via_ $node_c$ in order to reach $node_b$ **instead** of going directly from $node_a$ to $node_b$.
## Hardware
For this we will be making use of the [LillyGo T3S3](https://www.robotics.org.za/development-boards/esp32-lilygo-boards/H596) for each of our three nodes:
)In terms of antennas I will be making use of [these](https://www.robotics.org.za/communication-wireless-Industrial/antenna-866mhz/YN-868MHZ-5DBI) antennas. They seem to perform rather well and are easy to mount on any surface that is magnetic - which will probably make testing easy for accomplishing the topology shown prior.
)# Setup
## TNC
Firstly, plugin each RNode and then run the following command. After each successive command unplug the current RNode and plug in the next RNode:
```bash
rnodeconf /dev/ttyACM1 -T --freq 868000000 --bw 250000 --txp 20 --sf 8 --cr 6
```
After this each RNode will be placed in TNC mode.
Next, let us start up our TNCs. Run this on each node:
```bash
sudo ./tncattach /dev/ttyACM1 115200 --ethernet --ll -vvvv
```
## Version of babel
For these tests we were using the `1.13.x` series. Anything where the the $x$ in `1.x.y` is different is incompatible.
You can build `babeld` with the following:
```bash
sudo apt install build-essential -y
git clone https://github.com/jech/babeld
cd babeld
git submodule init
git submodule update
make
sudo make install
```
## Babel
Firstly, let's revise what the Babel filter should be per each node. This should be saved to a file named `filter.txt`:
```
redistribute local ip 0.0.0.0/0 ge 0 deny
redistribute local ip fd00::/8 ge 64 allow
redistribute local ip ::/0 ge 0 deny
```
Now let us start Babel on $node_a$ and $node_c$ like this:
```bash
sudo babeld -d 5 -H 5 -c filter.txt tnc0
```
We start Babel on $node_b$ like this so that we can expose the control port which `babelweb` will use in order to get routing information from:
```bash
sudo babeld -d 5 -H 5 -c filter.txt -g 3001 tnc0
```
Let us also start `babelweb` on $node_b$ with the following:
```bash
./babelweb2 -static bweb/static/ -node [::1]:3001
```
We can confirm it is running by visiting `http://localhost:8080/` in your web browser.
# Testing
Let's begin testing.
## Assigning some addresses and _making some routes_
Let's assign the following addresses to the `tnc0` interface on each of our respective nodes:
1. $node_a$
a. `fd20::1`
2. $node_b$
a. `fd20::2`
3. $node_c$
a. `fd20::3`
b. Note: We don't need to do this for forwarding to work, the forwarding address used is the link-local one and that is used for link-layer (MAC) address resolution when constructing the Ethernet frame for forwarding
We can do this easily on each node as such:
```bash
sudo ip addr add <ip> dev lo
```
Yes, I am adding it to `lo` - it doesn't matter. The address just needs to be assigned to _some_ interface in order for it to be assigned to the host (and of course picked up by babel for advertising). **Also**, it is a full `/128` that will be generated. We are not doing any sub-netting at each router where hosts behind it are non-babel nodes - therefore this is perfectly fine for our use case. Our assumption is that each host _is_ also a router.
## Tests
Here we do some tests.
### Test 1
The antennas used were:
* $node_b$ long-pole
* $node_c$ long-pole
* $node_a$ magnetic-base
In this test I, $node_b$ (my laptop), was sitting next to $node_c$ and as we can see from the tests, it appeared that I had direct reachability to both $node_b$ and $node_a$:
){:height 379, :width 659}### Test 2
The antennas used were:
* $node_b$ long-pole
* $node_c$ long-pole
* $node_a$ magnetic-base
Here I got up with my laptop ($node_b$) and then moved to the middle of the house, effectively between both antennas.
We can see a few things start to happen here. The neighbour relationship between my laptop ($node_b$) and $node_c$ stopped, the hellos being sent by either router were not being received. It is via this mechanism that reachability will drop every 5 seconds (when an advertisement is not received within the `hello_interval` then the reachability starts to drop at each time window):
){:height 362, :width 659}We can also see from above (and below) that the new routes for $node_b$ got installed. Meaning that in order for $node_b$ to reach $node_c$ it must first go through $node_a$. In fact we can see this here in the ttl values (purple ones):
)It seems the tests were a success! 🎊️
# Automation
## Startup executables
We can neaten up things a little to make our setup more automatic. By this I mean automating the startup of `tncattach` and `babeld`. This can be accomplished with a systemd unit (on SystemdD systems of course).
Create a file named `/etc/systemd/system/tncattach.service`:
```
[Unit]
Description=tncattach
After=network.target
[Service]
ExecStart=/usr/local/bin/tncattach /dev/ttyACM0 115200 --ethernet --ll
[Install]
WantedBy=multi-user.target
```
Create a file named `/etc/systemd/system/babeld.service`:
```
[Unit]
Description=babeld routing daemon
After=tncattach.service
[Service]
ExecStart=/usr/local/bin/babeld -H 5 -c /home/deavmi/filter.txt tnc0
[Install]
WantedBy=multi-user.target
```
Make sure to adjust any paths above including **binary executable paths** and **configuration file paths**.
Now run the following commands to start both services now and install them into their target - of which will be the target that runs on boot-up:
```bash
sudo systemctl enable --now tncattach
sudo systemctl enable --now babeld
```
## Automating addressing
Let's also have the IP addressing automatically configured.
On $node_a$ create a file in `/etc/netplan/lo.yaml` with the following:
```yaml
network:
version: 2
ethernets:
lo:
addresses:
- fd20::1/128
```
On $node_c$ create a file in `/etc/netplan/lo.yaml` with the following:
```yaml
network:
version: 2
ethernets:
lo:
addresses:
- fd20::3/128
```
As for $node_b$ (which is my laptop) I will not be automating it.