Change from Class C to Class A

[techalum]

Hello all! Newbie network guy here. I seem to do the phones but always get called to do network stuff. So hear is an easy one for you. We have a class c network and have just run out of addresses. The company wants to move to a class A subnet. My thought is that I can change the IP on all devices, clean out the DNS entires and clear all devices of their class c addresses. It seems like just a lot of manual work. A server will still hand out addresses.

So... Is this the most basic, easiest way to accomplish this? Are there other ways to do this? Please let me know what you would do along with any of your thoughts.

 

[jimbopalmer]

Assuming you have most of the machines on DHCP, update the DHCP server to a 10.x.x.x address with a subnet of 255.0.0.0

Then manually update the servers and printers.

I tried to remain child-like, all I acheived was childish.

 

[jimbopalmer]

Mind you, I would have formed a second class C network, myself, less broadcasts. We wound up with 42 class C subnets. Often one per floor, or one per building.

I tried to remain child-like, all I acheived was childish.

 

[dearingkr]

My 2 cents...

I completely agree with jimbopalmer on this.

I'm not a fan of having more than 200 devices per subnet.
Especially if you are redesigning it from scratch.

For example, at any site where you have a large number of devices, you can divide them up geographically (bldg1, bldg2, floor1, floor2) or functionally (accounting, sales, engineering).

There are several advantages to doing this:

1. Better network performance; smaller broadcast domains mean better performance.
2. Easier troubleshooting; simpler to track down malfunctioning devices.
3. Enhanced security; for instance, does everyone at that site really need access to accounting resources?

MCSE CCNA CCDA

 

[techalum]

What about the router? Wouldn't that need to be changed as well? How would I create a second class C without having a second DHCP server? PLease excuse my basic questions. I am a phone guy trying to survive a network project. Here is something I just found out... We already have devices using a 10.x.x.x subnet. So I guess all I need to do is change the DHCP scope on the server? These devices are set as static. Obviously that means there is some sort of access-list ( I am googling this information) already set up? I am just looking for a precise way to do this and make myself the hero.

 

[dearingkr]

Your server can have multiple DHCP scopes.

MCSE CCNA CCDA

 

[burtsbees]

What kind of router? Usually, dhcp servers can hand out multiple pools...
You can use a ten dot subnet, and have multiple 10 dot subnets, and use a /24 mask as well. I third the opinion of jimbopalmer---use /24 subnets, to minimize broadcast traffic, and just to have separate broadcast domains. This is one advantage of VLANs, actually, and you're essentially doing the same.

Burt

 

[techalum]

i appreciate your help and hate to beat you down with these basic questions.
burtsbees, it looks like you are saying i do not need to make changes to a router or create a vlan? is there a document that can walk me through all of this? I hate to lean on everyone so much. But I will take as much help as I can get. If I can go without changing the router, firewall or switch, that would be ideal. But I will obviously do whatever it takes. As far as multiple class c's. i could have a 192,168,169.x as well as a 192,168.168.x

 

[dearingkr]

I think some changes to the router are unavoidable.
At the very least, it is your default gateway, and must reside within the subnet(s).

We can offer you more specific advice if we had more info about your network equipment and how the network is set up.
For instance:
Mfr & model of router
Mfr & model of switches
Mfr & model of firewall, if any
IP range(s) you are currently using


MCSE CCNA CCDA

 

[burtsbees]

Not necessarily dearing---he can simply use a /8 for routing, and the new devices put on a /24, and he will have to change all other devices to at least the remaining /16 on up, but I would of course put them on a /24. The access lists or routing statements can just have a supernet which covers all subnets.
We do need a diagram/topology though...

Burt

 

[techalum]

Thanks guys. I have attached a basic topology in word. I will be brief with the description below.

Our connection begins with a 2600 series cisco router which is maintained via Air Band. We then have the following:
VoIP phone switch on the outside
Firewall (sonic wall)
then a WAN accelerator
Followed by the wan accelerator there is a core switch. 4 more switches connect to the core. 3 are for users and printers. the fourth is for all of the servers. Socrates server hands out the addresses.

 

[burtsbees]

Where's the link or attachment?

Burt