Changing subnet masks and connectivity during transition..

[OutToLunch]

I think I really should know the answer to this one, but my brain isn't working today (or yesterday!)

Currently, we have 1 physical set of cabling, 2 networks running on it, no managed switches/VLANs or anything clever, just DHCP for the curriculum network and static IPs in a different IP range for admin.

192.168.0.x (255.255.255.0) - dynamic IPs/curriculum
192.168.16.x (255.255.255.0) - static IPs/admin

Admin machines that also need to access the curriculum network end up having to have a second static IP from the curriculum range set too. It's all getting very clunky, IP conflicts when old machines are suddenly plugged back in etc.

What I would like to do is expand the IP ranges available but with minimum immediate impact - there's only me here, and a hundred or so machines I could would have to run round to set any back to DHCP etc.

So, onto the dumb question -

Rather than playing with partial bits of masks, I was thinking of just moving the whole network to 192.168.x.x (255.255.0.0) so I can start changing things to a more logical layout - eg. 192.168.1.x WAPs, 192.168.2.x Networked printers...

Is there any gradual way to make this change without immediately stopping everything talking to everything else? e.g change the DHCP subnet mask first, let it start allocating IPs in a new range - would the newly allocated IPs still be able to talk to static IP things like printers which would fall in the same range - and more importantly would the printers etc still on 255.255.255.0 be able to talk back?

Advice appreciated from anyone who's already done something like this, or could do something like this blindfolded and is wondering how I'm even a nm

[SYNACK]

If you changed the subnet mask to 255.255.0.0 and left the allocations in the 192.168.0.x range at the start this should allow all of the DHCP machines to talk to the older stuff and anything new that you assigned, once you finniched teh assignment you could change the allocation on the DHCP to whatever you actually wanted the hosts to be.

192.168.x.y is actually a class C private address so technically it should be broken up into 254 host chunks but it should not cause any problems.

As to the multiple IP addresses have you thought about setting up RRAS (routing and remote access) on a windows server to route between the two networks. This would not require any fancy switch setup just pointing the default gateway of the staff machines to the RRAS server IP. This would allow you to split up the networks with subnets in case you wanted to further segment them in future.

[Jay]

Enlarging the subnet mask should affect anything currently in place. Your machines on 192.168.0.X will still be able to talk to anything else on 192.168.0.X. You only need to worry if you make the mask smaller.