staticrouter

The staticrouter program is a small utility to help people looking to distribute static classless routes to network clients via DHCP using their routers.

This is generally done via DHCP option 121 as defined in RFC3442, and a number of advanced home routers let end users set this. Unfortunately, the interface to set this up is generally kind of clunky, and requires using a fairly obtuse, hexidecimal based notation that is easy to get wrong. With staticrouter, hopefully the potential for error can be significantly reduced.

The utility was inspired from this Javascript app on Medo's homepage. It doesn't share any code, but the basic functionality and output are essentially identical.

Usage

The program reads route information from a text file on your computer. The format of the text file should match:

<default gateway ip>
<network 1> <gateway for network 1>
<network 2> <gateway for network 2>
<network 3> <gateway for network 3>
...

As an example, say that your network's default gateway is 192.168.3.1. Additionally, let's assume you have two VPNs into this network. The first VPN uses network 10.2.3.0/24 with a gateway of 192.168.3.2, and the second VPN uses network 10.4.5.0/24 with a gateway of 192.168.3.3. If this was your setup, you would make the file routes.txt (which we'll be using as an example here) as follows:

192.168.3.1
10.2.3.0/24 192.168.3.2
10.4.5.0/24 192.168.3.3

You would then run the following from your shell:

$ staticrouter /path/to/routes.txt

The resulting output

00:c0:a8:03:01:18:0a:02:03:c0:a8:03:02:18:0a:04:05:c0:a8:03:03

is the hexidecimal format needed for Ubiquiti/Unifi and OPNsense routers for those classless routes.

The utility also accepts a command line argument -format which can have the following values:

• ubiquiti: Outputs format for Ubiquiti / Unifi routers (this is the default)
• opnsense: Identical to ubiquiti as the format is the same for these routers
• dhcp: Outputs the format defined in the RFC
• mikrotik: Outputs the specific commands needed for Mikrotik routers

For example:

$ staticrouter -format=dhcp /path/to/routes.txt
0x00C0A80301180A0203C0A80302180A0405C0A80303

$ staticrouter -format=mikrotik /path/to/routes.txt
/ip dhcp-server option
add code=121 name=classless-static-route-option value=0x00C0A80301180A0203C0A80302180A0405C0A80303