Adding IP's to Private LAN

[T3st1ng]

My company recently downsizes, and I have inherited all technical issues, although I don't have a technical background, so please pardon me if my question seems stupid.

Computers on the network have 10.2.0.1 to 10.2.0.254 assigned to them. I need to add about 400 more IP Addresses but cannot change any part of the existing address scheme. Machines from the one IP range will have to be able to communicate with the other and vice versa. I have no idea where to start and what steps I would need to take.

There are Cisco Switches and a Firewall in place.

Please help.....

 

[LloydSev]

400 more IP Addresses?

Can you please post the SubNet Mask for an individual machine on your network?

What you would need to do, depends upon that 1 #.

Do an "Ipconfig /all" from a command prompt.

In Windows XP/2000, the command is "cmd" at a Start -> Run prompt.

In WinME, 98 or 95 it would be "command" at a Start -> Run prompt.

Computer/Network Technician
CCNA

 

[T3st1ng]

255.255.255.0

 

[LloydSev]

Are you familiar with changing subnet masks?

You could change that to a 255.255.0.0 and at that point pick up 64516 IP Addresses for use without the need for additional hardware.

And that is of course, not using addresses 255 or 0.

Computer/Network Technician
CCNA

 

[T3st1ng]

I've been doing as much reading as I possibly can. Adding too many IP's could potentially degredade the performance of the network, right?

I tried using a subnet calculator and plugged in the desired nodes as 1024, which gave me a subnet of 255.255.252.0. Would this work?

If so, how would I know what my available list of IP's would be?

Thereafter, would I need to make any changes on my firewall to make it aware that traffic to and form these addresses need to stay internal?

 

[manarth]

T3st1ng - with this subnet mask you are limited to 254 machines on the subnet.

If you change the subnet mask to 255.255.0.0, you have 65534 possible machines on the same subnet: using the same addressing scope, you have IPs 10.2.0.1 to 10.2.255.254.

Here are some (old!) posts relating to subnetting:[ul]
[li]thread581-776397[/li]
[li]thread581-543461[/li]
[li]www.learntosubnet.com[/li]
[/ul]

Note: I deliberately suggested the subnet mask 255.255.0.0 because (without knowing makes/models concerned) there is no knowing if the configuration would support a more contained classless configuration - hence choosing the next classful mask.

Hopefully you're running DHCP, in which case you simply change the scope on your DHCP server. Review your firewall rules - these may need updating. Your switches should not be affected.

<marc>

 

[LloydSev]

that depends on the current configuration of the firewall.

Also, it's not the adding of to many IPs that would degrade performance, but the adding of to many hosts that would degrade.

Also, let's keep this discussion here, as this is more a TCP/IP issue than a Cisco issue.

Computer/Network Technician
CCNA

 

[manarth]

Doh! Looks like my post slipped behind a bit

T3st1ng - without knowing your firewall rules, there's no saying if they need updating or not. It's quite likely though!

As for the subnet mask 255.255.252.0, this should work, as long as all your existing hardware supports CIDR (Classless Inter-Domain Routing). If not, sticking to conventional classful allocations is a safe bet, and unless you have significant bandwidth concerns, the network degredation shouldn't have much of an impact.

<marc>

 

[bcastner]

Adding too many IP's could potentially degredade the performance of the network, right?"

Will not make a darn bit of difference. Now adding 400 new workstations is a different fish.

 

[T3st1ng]

How would I go about creating a separate subnet that can communicate with my existing one? I currently have a Cisco PIX.

 

[T3st1ng]

Also, right now everything is static.

 

[LloydSev]

Adding another subnet?

That would depend on the physical setup you want.

Will both networks use completely SEPERATE network equipment? Or will they both be plugged into the same switches, etc..?

Computer/Network Technician
CCNA

 

[manarth]

I imagine you want to add another subnet in order to avoid having to change the 254 current machines IP settings.

In all honesty, now is the time to change to DHCP and sweat through changing all the current machines.

In fact (assuming you're running windows) windows' default configuration is set to use DHCP, so you'll only have to manually configure the 254 old machines, instead of 400 new machines.
(And you won't even have to think about it when the next 400 machines come along!)

<marc>

 

[LloydSev]

I would just use the 10.0.*.* networks with a subnetmask of 255.255.0.0 and just change the rest of your clients to DHCP so that your DHCP server would hand this out to everyone.. this way you don't need to add any additional hardware.

Computer/Network Technician
CCNA

 

[T3st1ng]

These new machines will eventually be moved to a second site to be connected by an IP VPN. Therefore, they will eventually be using different hardware.

So as not to affect any feedback, I am 100% fine with changing my existing 254 machines. That's not a concern. I just want to make sure I do things the right way going forward.

 

[RookThis]

Here are my two cents.. It would help if you include your topology, what type of switches you are using etc... The simple solution would be to create a new subnet and let a routing protocol handle communications between the subnets. Creating a larger subnet makes for a bigger spanning-tree and more broadcast traffic etc... One good thing about this stuffis that there are many ways to get the same result, the difference about the solutions is how efficient one wants to make the design.

In the end it's all good!