It sounds as if what you really want to do is create a new subnet or two. Rather than increase your netmask size, create a routed network, with subnets off of each interface on your router(s). Then you set up routing and the only thing that you have to change is to have routes defined on your router and dhcp scopes for each of the subnets.
I'm not sure off-hand how you define the scopes appropriate for your subnets other than having connections to each of the subnets from your dhcp server and having it issue addresses based on interface. Maybe someone else out there knows a fancier way to do it.
In my experience, subnets larger than a class 'c' get quickly bogged down by the number of broadcast and unicast packets on the network and really slow down. Subnetting and routing solve these problems. But you have to create an architecture that is friendly to routing. If your Internet connection and all of your servers go out the same interface on the router and there is not any peer-to-peer traffic, then you really haven't solved your congestion problems, you've simply made them more complex.
I assume that you have more than one server with that many clients, so you need to subnet based on which clients need access to which servers most of the time. Then traffic is mostly localized (maybe not even having to go through the router). Also, move your internet connection to a separate interface on the router. This solution will require you to modify much more than simply the router configuration, but it will provide far superior performance than simply increasing the netmask size.
pansophic
