Public to Private IPs

[thefarewellnote]

I have a client that had their network setup about 10 years ago with a public facing IP. Basically all their workstations/servers all have an IP that 75.74.43.210 (not their actually schema). They don't own these IPs at all and we are replacing their servers now with new hardware. What would be the best solution to move them off of the public ips to a private schema.

We can't interupt their business so I was thinking of setting the new servers up. Giving them a new private IP such as 192.168.1.xx and then adding a second IP to that adapter. This would allow us time to migrate data over and then when completed turn off DHCP on the old servers that are handing out the public facing IPs and turn on DHCP on the new servers.

That should work correct?

[sc302 Veteran]

They can't all have an ip of 75.74.43.210. If they do then that is natted and therefore you are fine. If you are telling me that they have 75.74.43.x that is a different story. 1 ip address per device, unless it is natted then you have 1 ip address for multiple devices.

An ipconfig from each workstation should show what IP each workstation has. IMO it is probably doing some sort of one to one nat for some sort of remote support and each workstation does not have a external IP assigned to the nic.

Take a weekend and do it right. They shouldn't notice anything if you plan accordingly. If you plan on doing this during the week, they need to expect outages or put the new server on a new switch and the old server behind a different switch and use vlaning on the new switch to route traffic between the networks to get your job done, then you can do it one by one on your own time moving the users from the old switch to the new once you have migrated their data and domain over. This would probably be the cleanest IMO.