Network Change-Over

Clarifications

come up with your range and plan on paper, find out what each server you want to change the IP address to be. Run a complete back up of all the servers. And over the weekend when no one is there, implement the plan, and test it all. If its not working by Sunday I would start to restore from the backups.

In need of Help

what kind of services on the network do you have?? Would be a better question to ask... Do you have an exchange server, or DNS running, print server ect?

Edited: oops, it took me awhile to write this with phone interruptions, and the topic's already been covered.

So you're saying that you need more than 253 hosts in your network and need to change to a class A?

To re-IP a network is indeed a disruptive process so should be scheduled for off-hours. Obviously the number and type of equipment on your network will determine how long the process will take to settle out, and also how organized the network is to begin with, will affect the downtime.

In its simplest form, what you said is true, but I'll go into a little more detail.

Start with an inventory of all static equipment, i.e. routers and all managed switches, WAPs, servers, static printers, etc. Also look at your DHCP pool(s).

Next, plan the new network so you don't run into this again. Logically slice up the new network into several categories and map it out: routers / network equipment / static printers / servers / other static equipment / DHCP pools / "other" / etc.

Plan any routing changes

Now that you know where you're going, yes start with the servers and routers, particularly the DCs, DNS, and DHCP server(s), routers. The DHCP MMC doesn't handle DHCP server IP changes very well. Chances are you'll have to drop the DHCP server from any MMC you have it added to, re-add it, re-Authorize the DHCP server and de-activate the old scope. Make sure all of the servers are happy and are populating DNS with their new IP's -- though the servers don't tell you to, when I'm doing a re-IP, I like to reboot the servers and have them boot clean on the new IP. Inspect your AD DNS zone and remove any stale entries for the servers. Make sure all of the servers are happy and resolving each other.

Create the new DHCP scope and Re-create any reservations you have on the old scope with their new IP's but I wouldn't activate it yet.

Now that the core servers and routers are done and tested, make sure they can route to other networks and the internet, then work on other servers, Activate the new DHCP scope, and start working on managed switches, static printers, etc. and start testing workstations and user functionality.

just go to 192.168.x.x? Would that be too easy?

This may be a less disruptive option for you, but without knowing your network it's hard to say.

But if your switch/router can handle 802.1q tagging, you can run multiple networks (vlans) on your switch and create a "router on a stick" to handle the inter-vlan routing.

This way you could leave the existing network the way it is, create a new network on your router, then slowly migrate devices to the new vlan. This would involve creating a new DHCP scope, switch changes, and router changes....but the devices could be moved over at your leisure.

Just a thought.

If you did this, 90+ percent of your network would be lumped in the 192.168.165.x range of your expanded 18-bit network. Sure it would work fine, but your IT friends will make fun of you, whether they tell you or not. :-)

You will still have to touch every static device on your network to change the mask because as soon as you start creating devices outside of the 192.168.165.x range, something in the 165.x range with a lingering 24-bit mask will not be able to communicate with those new devices outside of the 165.x range.

However you do it, Class A, Class B, 18-bit CIDR, whatever ... organize it, plan it, and bite the bullet and spend the evening or the weekend and change it once.

Having said that, I do however agree that this is a good compromise. With the 192.168.128.0/18 network, you could leave all of your static IP printers and such in the 165.x range, move everything else out of that range accordingly per your new network structure, and then you only have to touch the statics to change the subnet mask (and probably a new router IP), but you wouldn't have to change the shared printer IP's on the servers for example.