How to change internal IP scheme on production network?

192.178.x.x/16 and 192.188.x.x/16 ranges are not for LAN usage, would causes routing problems. Consider use 172.16.0.0/16 and 172.17.0.0/16 (per example)

Hello Miguel,   These aren't my true IPs just using for example to show overall goal and looking for suggestions on steps i.e. do I do DC first, routers first, firewalls first or start clients and static first and roll to network gear?  

If somebody has done this they may have list of steps that worked they could share.

This wont be a problem if you can schedule a downtime change. We do not have your network detail, however which we should notice is:
- DHCP
- Default Gateway
- NAT and Access Rules on Firewall
- Then change subnet mask / IP on devices currently set static IP address

Since you have several locations keep in mind that routing needs to updated also and VPN tunnels if used.
Also keep in mind printers and other equipment with static IP that need to be changed.

I would also like to advice to subnetting each /16 into /24 to limit L2 domains.

You should also if doing L3 segmentation take into consideration any crAPPLE devices that need to be reachable via L2.

@Donboo - yes I plan downtime, but the order you would do is:
DHCP scope
Firewall (VPN tunnels)
Static devices (servers and printers)
Last switches and routers

Can you elaborate on the recommendation to limit L2 domains and crApple devices?

I normally use /24 for each subnet so I dont get too big a broadcast domain. Of course this is depending on what kind of clients and host use the network but looking at Windows clients they tend to broadcast a lot. Also printers may use proprietary protocols  that broadcast packets you dont want but you are unable to turn off as this is what the vendor wants.

In regards to crAPPLE devices they use bonjour to locate each other and say you have a TV and you want you other Apple devices to be able reach it via airplay function then you either need them to be on the same IP net or somehow bring the L2 multicast over L3.

So what traffic would you recommend to vlan apart:
1. Servers/Network
2. Clients
3. Printers
4. Apple

I'll keep the /24 in mind.  What do you do for roll out order?
Do you start with
1. Lower DHCP Lease
2. Change DNS and DC server
3. DHCP Configuration
4. Servers
5. Printers
6. Sites and Services
7. IIS
8 . Applications
9. WAN/VPN tunnels

Or is there a template of the best order to make the changes

Thanks for the feedback