oe7drt-website/content/posts/2022-11-21-hamnet-on-the-pfsense/index.md

+++
title = "HAMnet on the pfSense"
summary = """A short guide on how I installed my L2TP tunnel on my
router/firewall. Routes get announced to new DHCP clients."""
date = "2022-11-21T20:13:08+01:00"
#lastmod = ""
categories = ["amateur-radio"]
tags = ["hamnet","pfSense","networking","linux"]

+++

The usual approach to connect your computer to the
<abbr title="Highspeed Amateurradio Multimedia NETwork">HAMNET</abbr> is to
create a <abbr title="Virtual Private Network">VPN</abbr> tunnel using
<abbr title="Point-to-Point Tunneling Protocol">PPTP</abbr>. Most of recent
operating systems stopped supporting this protocol because it is outdated and
insecure.

In my recent
[post about HAMNET]({{< ref "2022-10-16-vpn-tunnel-into-hamnet-on-fedora-36" >}})
I created an <abbr title="Layer 2 Tunneling Protocol">L2TP</abbr> tunnel to the
german VPN Server at the RWTH Aachen University on my laptop. Routes have been
added manually---the network was only available on this particular computer.
No other device was able to connect to the HAMNET.

Now I made some changes to my home network where I finally was able to create
the tunnel on my main router/firewall.

## Creating a new <abbr title="Point-to-Point Protocol">PPP</abbr> device

Select <kbd>Interfaces</kbd> → <kbd>Assignments</kbd> → <kbd>PPPs</kbd>

![screenshot showing the top menu](01_create-ppp-interface.png)

Click on the green <kbd>+ Add</kbd> button on the bottom right and create the
new PPP interface with the following specs:

| Settings name | value |
| :--- | :--- |
| Link Type | **L2TP** |
| Link interface(s) | **WAN** |
| Username | **N0CALL** (your callsign usually) |
| Password | (your password) |
| Local IP | (leave empty) |
| Gateway IP or hostname | **vpn.afu.rwth-aachen.de** |

<!-- You can change `vpn.afu.rwth-aachen.de` with the IP address of the server if you
like. That may help if you don't have a working DNS setup in your network. At the
moment the DNS entry points to `137.226.79.99`. -->

![screenshot showing the PPP configuration](02_create-l2tp-interface.png)

## Create a new L2TP device

![screenshot showing device configuration](03_interface-assignments.png)

My screenshot looks a bit different because I have already assigned the
interface. You should see the option <kbd>Available network ports</kbd> in the
last row combined with a green <kbd>+ Add</kbd> button on the right side (just
below the red buttons). Select the newly created L2TP interface (which should
look like `L2TP (igb0) - HAMNET_VPN` -- or something like that) and click the
green button.

Then click on the new interface and set it up.

| Settings name | value |
| :--- | :--- |
| Description | **VPN_HAMNET** (a meaningful description) |
| IPv4 Configuration Type | **L2TP** |
| IPv6 Configuration Type | **None** (or SLAAC if you use IPv6) |
| Username | **N0CALL** (your callsign usually) |
| Password | (your password) |
| Remote IP address | **vpn.afu.rwth-aachen.de** |

![screenshot showing interface configuration](04_interface-configuration.png)

## Add static routes on the firewall/router

Click on the green <kbd>+ Add</kbd> button on the bottom right. Add the
networks `44.0.0.0/9` and `44.128.0.0/10` to the list; use the interface from
above as the gateway.

![screenshot showing routes setup](05_routes.png)

## The tunnel should be up and running

Go to <kbd>Status</kbd> → <kbd>Gateways</kbd> and look if it is online.

![screenshot of the gateway status page](06_status-gateways.png)

## Send this routing configuration to DHCP clients

We can send this configuration to DHCP clients when they get their IP address.

Go to <kbd>Services</kbd> → <kbd>DHCP Server</kbd> and select the interface
that you want to configure with these routes. Then scroll down to the section
<kbd>Other Options</kbd> and look for the last setting
<kbd>Additional BOOTP/DHCP Options</kbd>. Those settings are hidden per default,
so click on <kbd>Display Advanced</kbd>. Below you can now enter the additional
configuration.

You see three fields, <kbd>Number</kbd>, <kbd>Type</kbd> and <kbd>Value</kbd>.

| Number | Type   | Value |
| :---   | :---   | :--- |
| `121`    | `String` | `09:2c:00:c0:a8:0a:01:0a:2c:80:c0:a8:0a:01` |

{{< alert >}}
Do not copy this configuration into your pfSense. This setting is somewhat
encoded and routes the HAMNET IPs to my routers IP address. You have to create
your own configuration!
{{< /alert >}}

Create your own configuration with help of this script:

~~~bash
#!/bin/bash
check_ip(){ 
  local n=0 val=1
  for i in ${1//./ }; do 
    [ $i -lt 0 -o $i -gt 255 ] && val=0
    n=$[n+1]
  done 
  [ $n -ne 4 ] && val=0
  if [ $val -ne 1 ] ; then
    echo "Invalid IP: $1" >&2
    exit 1
  fi
}

to_bin(){
  local BIN=({0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1})
  for i in ${1//./ }; do
   echo -n ${BIN[$i]}
  done
}

while [ $# -gt 0 ] ; do
  nw=${1%/*}; nm=${1#*/}; gw=$2
  check_ip $nw; check_ip $gw
  if [ ${#nm} -gt 2 ] ; then
    check_ip $nm
    nmbin=$(to_bin $nm)
    if echo $nmbin | grep -q "01" ; then
      echo "Invalid netmask: $nm" >&2
      exit 1
    else
      nmbin=${nmbin//0/}
    fi
    nm=${#nmbin}
    echo $nm
  fi
  gwhex=$(printf "%02x:%02x:%02x:%02x" ${2//./ })
  nwhex=$(printf "%02x:%02x:%02x:%02x" ${nw//./ })
  nmhex=$(printf "%02x" ${nm//./ })
  [ $nm -le 24 ] && nwhex=${nwhex%:*}
  [ $nm -le 16 ] && nwhex=${nwhex%:*}
  [ $nm -le 8 ]  && nwhex=${nwhex%:*}
  echo -n $nmhex:$nwhex:$gwhex
  shift 2
  [ $# -gt 0 ] && echo -n ":"
done
echo 
~~~

Source: [mgergi.hu](https://mgergi.hu/en/it-blog/static-route-dhcp-pfsense)

Script was cited/hardcopied because I hate it when linked websites ain't
available any more. But there is a nice explanation on that website that
you should read.

Replace `192.168.10.1` with your routers IP address!

~~~console
$ hexroute.sh 44.0.0.0/9 192.168.10.1
09:2c:00:c0:a8:0a:01
$ hexroute.sh 44.128.0.0/10 192.168.10.1
0a:2c:80:c0:a8:0a:01
~~~

You see, you get two values. All you have to do is concatenate those two values
and separate them with colons. Insert the new string into the <kbd>Value</kbd>
field and save those options.

![screenshot of the DHCP server options](07_dhcp-server.png)

## More resources

* https://support.aa.net.uk/L2TP_Client:_pfSense
* https://id3145.com/2017/blog/5-pfSense-Add-Static-Routes-to-pfSense-DHCP-Clients.html
* https://www.iana.org/assignments/bootp-dhcp-parameters/
* https://www.rfc-editor.org/rfc/rfc3442.html