DHCP SuperScope

[ankit0680]

Hello,
I think this is a simpel solution but I am not totally grasping it.
We have a internal IP range of 10.10.20.x. .1-.99 are reserved for servers, printers, AP, Switches, ETC. We had made the scope for 100 - 254. The problem now is we are running out of DHCP address's. what is the best solution. I was thinking of redoing my DHCP scope, to make a super scope one 10.10.20.x for my Statics, and 10.10.21.x for my dynamics. Is this optimal ro what other options do I have that wont require major downtime. if it helps I am running Sonicwall 3060 as a firewall, and a Cisco 2650 XM router.
Kind REgards,
Ankit Parikh

 

[WhoKilledKenny]

What is the subnet mask of your network?

 

[ankit0680]

255.255.254.0

 

[chipk]

That subnet mask should give you 510 usable addresses, but you only seem to have mentioned 254 (20.1-99 and 20.100-254). You should be able to include 10.10.21.1 through .254 in your scope without superscoping.

 

[ankit0680]

Thats Great. I know this is NewB, How do I add the second scope?

 

[chipk]

Sorry, I guess I'm not explaining clearly.

When you have a 255.255.254.0 subnet mask, you have basically "split" the address range into chunks. These "chunks" are not just 0-254. For instance, if you subnet your class A (10.x.x.x) down how you have it, networks would be:

10.10.0.0
10.10.2.0
...
10.10.20.0 <---your network
10.10.22.0
10.10.24.0
etc.

The 10.10.20.0 255.255.254.0 network has an inherent address range of 10.10.20.0 through 10.10.21.255. Usable addresses on this network are 10.10.20.1 through 10.10.21.254. That's 510 addresses in a SINGLE scope. Therefore, there is no need to add another scope, you just expand your current scope in DHCP to include addresses in that range.

If you go into your scope properties in DHCP Manager (assuming you have a Windows 2k or 2k3 DHCP server), you should be able to expand your scope beyond 10.10.20.254. Windows DHCP won't let you specify an invalid address, so, if what you've said here is all correct, you should be able to just go to properties, and change the "End IP Address" to 10.10.21.254 (though you may want to do a smaller chunk at first). If on the other hand, you've accidentally left out some information, don't worry, you'll get an error saying that your address range is invalid and it won't let you expand it.

 

[WhoKilledKenny]

That is why I asked what your subnet mask was. If what ChipK is explaining does not make sense to you, do you have a Network Engineer that can assist? The concept of a superscope does not apply to your configuration. In fact most superscoping is done by ISPs to maximize an IP block.

 

[ankit0680]

HEy Guys,
Unfortunely I am the network engineer. This worked, I was just grasping the theory wrong. I think I am on the right page now., Thanks

 

[chipk]

So, what was the actual solution?

 

[ankit0680]

All I did was go into DHCP. And set the end of the range to 10.10.21.254. It seems to have worked.

 

[chipk]

Oh, ok. I thought you were saying you did something else.