Get the network interface card (NIC) from a known MAC address (and get the IP addresses on that NIC)

using System.Net.Sockets;
using System.Net;
using System.Net.NetworkInformation;
 
string localNicMac = "00:00:00:11:22:33".Replace(":", "-"); // Parse doesn't like colons
 
var mac = PhysicalAddress.Parse(localNicMac);
var localNic =
    NetworkInterface.GetAllNetworkInterfaces()
        .Where(nic => nic.GetPhysicalAddress().Equals(mac)) // Must use .Equals, not ==
        .SingleOrDefault();
if (localNic == null)
{
    throw new ArgumentException("Local NIC with the specified MAC could not be found.");
}
 
var ips =
    localNic.GetIPProperties().UnicastAddresses
        .Select(x => x.Address);