Query a DHCP server for a specified IP Addres to obtain MAC and hostname

Question

I have searched several forums and found various flavors of my issue. However, I can't seem to get good resolution. So here's the problem:

I am writing an app that collects IP Accounting data from Cisco Routers. The app collects only the Source, Destination, bytes, and packets. All of this information is stored in a SQL database.

The output of the IPA data is timed (Cisco cron jobs). My IPAHandler needs to be able to resolve IP Addresses to host names. I am doing this with some releative ease, until it comes to local IP Addresses of machines that are not joined to the domain.

We are a college and we have several "rogue" notebooks on wireless. We would like to be able to capture the machine name of each device that gets an IP address - subsequently we would have their network usage data. But if I try to use the code listed below I get an error:
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string sName = Dns.GetHostEntry(IP).HostName;
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Our AD only allows secure updates, so they don't show up in DNS and I get the following exception:
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No such host is known.
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Here's the question:

Can I query the DHCP server (an AD Domain Controller) for the IP Address and machine name? If so, do I need to use a WMI query, or is there an API I can use?