Expanding/Changing Existing DHCP Scope

[gclumpkin]

All:

I have inherited a network and need some advice on DHCP. The machine in question is a Windows 2000 server that is our domain controller, DHCP server, DNS server and Exchange 5.5 server.

The existing DHCP scope starts at 192.168.0.128 and ends at 192.168.0.192 with a subnet of 255.255.255.0. There are no reservations specified.

We are running out of available addresses so I need to do something soon. A Microsoft TechNet article states that you can expand the address range by increasing the end IP address for the current scope.

Why can't I change it to go from 192.168.0.1 to 192.168.0.254? That would give me plenty of addresses for now. Also, our servers are all statically set down in the first few addresses (192.168.0.1 through 192.168.0.5) but other static devices like printers are all over the place. If I increase the end of the range, with there be conflicts if a PC wants an address that a printer has?

Any help would be greatly appreciated.

Greg

 

[Smorgan11]

can't see the harm doing that. Or why not just delete the scope and create a new one. They are so easy to do!

 

[ShackDaddy]

Greg, I would either scan your network to see which IP's are in use in the 129-254 range or ping each of those and make sure you aren't getting any replies. If you find that some of your printers or other devices are in that range, just add 'exclusions' to your scope. Don't bother creating reservations.

And yes, just extending the range like you described is a good idea, but you'll need to do what I described above first.

Here are a couple of other things to think about:

-Changing your lease time down from the default of 7-8 days to 1-2 days. That may free up some leases and give you some breathing room.

-Do you have a remote access server in your network? If they are configured to use DHCP, they will often gobble a handful of addresses and hold on to them permanently, even if no one has dialed in for months. If you configure the RAS to hand out a specific range of static IPs (110 to 116, for example) instead of using DHCP, that would free up some addresses in your DHCP scope.

ShackDaddy

 

[gclumpkin]

Thanks for the help/advice guys. We added a few more addresses to the scope and got us some breathing room. I will most likely recreate the scope and move the printers and other static devices down near the servers.

We do have two servers that take up several DHCP leases for RAS. We are not using RAS here and I saw no way to uninstall/disable this service on either server.

Any ideas?

Again, much thanks for your previous replies.

Greg

 

[cyberspace]

I too would just extend the scope, theres really nothing to worry about once basic checks have been made.

As suggested by Shack Daddy, just scan the addresses between 1-127 and 193-254 to see wether or not you need to make any exclusions.

Instead of sitting and pinging all those times, you can use this tool, which will rapildy scan that range and immediately inform you as to wether there are any live addresses in the range:

http://www.angryziber.com/ipscan/

'When all else fails.......read the manual'

 

[gclumpkin]

Thanks cyberspace. I've downloaded it and will do just as you suggest.

Any ideas why the two servers keep taking up addresses with RAS? I cannot for the life of me see how to disable/uninstall this service on these two machines.

Thanks again,
Greg

 

[cyberspace]

There is a service 'Routing and Remote Access' - However I am not sure if that is directly related. For example, our IT Support company used to dial in with 56k modems, which required this service to be running. However, now they come in through an internet connection, and the service is now disabled!

I'm sure somebody else could help, but if you alter the range then you probably won't miss them anyway

'When all else fails.......read the manual'