These files are configuration files for "our" internal network.
It is highly non-trivial, so don't use this configuration as the basis of your network unless you know what you are doing.
It features: around 30 hosts, many of them have additional networks behind them and use an assortment of different tunneling protocols. The vpn is fully routed, no arp is used at all.
The public IP addresses of connecting nodes are automatically registered via dns on the node ruth, using a node-up/node-down script.
And last not least: the if-up script can generate information to be used in firewall rules (IP-net/MAC-address pairs) so ensure packet integrity so you can use your iptables etc. firewall to filter by IP address only.