We have a Windows Server 2008-based Active Directory environment. It's currently configured with all devices in the building on a single subnet (192.168.1.0/24). However, we're getting to the point of running out of available IP addresses. While I could try some stopgap measures such as adjusting DHCP lease times, I really want to find a more permanent solution.
The two options I've considered are either moving to a larger single subnet, or separating the building into two subnets. My first thought was just to increase the subnet size and keep everything together, but I'm worried about increasing the size of our broadcast domain and the potential performance impacts.
Everything now is ultimately feeding back to a SonicWALL TZ-210N router, which does have multiple interfaces and the capability to route between subnets, so I could do that without too much of a headache, but I'm worried about how that will impact Active Directory. In particular, I'm wondering if I'd need a separate domain controller for the new subnet or if it could still deal with the DC on the original subnet. Also, we have lots of servers that get accessed via UNC paths using NetBIOS names (e.g. \\server1), and since NetBIOS traffic doesn't normally get routed, I'm wondering if all our scripts, drive mappings, etc. would just break.
So I'm looking for advice. How would you handle this case, and what do I need to be thinking about?