G'day gardner1,
As far as I am aware Net::Pcap is only useful for "local" networks and not looking up foreign information. That is, you must be directly connected to the network, and have the traffic passing through one of your local network connections, either as a passive sniffer or directly routed traffic.

You could use something like Nmap to explore the remote networks and parse the information using perl into Nagios configuration files.

What information do you already have?

Neil