2nd subnet??

The_KiD · 22 Mar 2007 at 08:59

Right before we go any further, please remember to speak slowly and clearly. I can find my way round a network and and I can do a lot of things on them, however my knowledge only comes from me messing around with things, so I am no expert.

Ok here's the problem.

We are running out of Internal IP's on our work network. I think we have about 19 left EEEeeeek!

So how do I go about getting more internal IP's? and making sure they can all talk to each other ?

I think what I am looking for is called a 2nd subnet and our current internal IP is 10.0.10.X so I would set up a second subnet of 10.0.9.X for example, but how?

We use AD and DHCP and any help is greatly appreciated.

NiCkNaMe · 22 Mar 2007 at 09:16

Your looking to subnet your designated network address (10.0.10.0) to create additional subnets.

The person who set up your network originally should have catered for this, scalable networks, etc, etc

Need a bit more info before I could offer any suggestions mate. Your going to need a complete re-design of the network I reckon, what's your current topology? (Routers, switches, firewalls, hosts, servers, departments)

How many external IP's do you have? What interior gateway routing protocol are you running? Your routers will need reconfiguring to allow for the changes. It may be a sensible time (depending on the size of the company) to get a nice new network design done so your covered for any future changes. You could look at implementing VLANS to increase network performance whilst your at it.

matja · 22 Mar 2007 at 10:12

on machines with static IP's : change your subnet mask to 255.255.254.0
on the DHCP server(s) : change the lease subnet mask to 255.255.254.0 and modify the lease settings to include 10.0.11.*

effect : addresses 10.0.10.1 to 10.0.11.254 will be available (510 IPs) with no router craziness.

The_KiD · 22 Mar 2007 at 10:20

must say I like matja's idea more, would this be ok ?

The_KiD · 22 Mar 2007 at 14:14

matja said:
on machines with static IP's : change your subnet mask to 255.255.254.0
on the DHCP server(s) : change the lease subnet mask to 255.255.254.0 and modify the lease settings to include 10.0.11.*

effect : addresses 10.0.10.1 to 10.0.11.254 will be available (510 IPs) with no router craziness.

I just went to check out if this would be possible, but the subnet mask in the DHCP is greyed out.

How can I change it?

Johny Boy · 22 Mar 2007 at 15:02

Instead of a second subnet and all the pain that goes with routing between subnets you could just change your subnet mask to give you more addresses in a single subnet.

For example

IP: 10.0.0.0
subnet: 255.255.255.0

= 255 addresses

subnet 255.255.0.0

= 65025 addresses

And they are all on the same subnet so you don't have to worry about doing routing between two seperate subnet.

Not ideal if you filled all 65025 as your network would become saturated with broadcasts and the like.

But for just adding a few more machine that would do the job.

The_KiD · 22 Mar 2007 at 15:06

Good plan, however as my last post says, I don't seem able to change the subnet

Johny Boy · 22 Mar 2007 at 15:07

yeah sorry I just noticed that and was having a fiddle in DHCP settings here

Johny Boy · 22 Mar 2007 at 15:15

By the looks of it you can only set the subnet mask when creating a scope.

You will need to recreate the scope from scratch to change the subnet mask.

Unless someone knows better only way I've found of doing it.

The_KiD · 23 Mar 2007 at 08:43

*BUMP*

Anyone know if what JonnyBoy says is correct? Looks like it is, but would hate to go through all this hassle to find out it wasnt.

Oh and thanks all