Best Practices

A little more detail of the makeup of your network would be helpful.
1. What is providing your DHCP scopes, server or other device?
2. Are your switching devices capable of multiple VLANs?
3. What will provide the routing and can it route to different VLANs?

I'm sure people would argue here but would it not be easier to modify your existing subnet to a /23 and give your scope a greater pool of addresses. - Druis 7 years ago

I agree with the suggestion of using a /23 (255.255.254.0) subnet. I've been using that for years and it's works with all of the hardware and software I currently support (years ago I saw some items that wouldn't allow it). To supernet two class C subnets, you'll need to change the third octet, which will need to start with an even number (not odd one). i.e. 192.168.0.0 and 192.168.1.0, not 192.168.1.0 and 192.168.2.0.

If you're using DHCP, you may need to delete the scope and recreate it. If you do that, I'd suggest changing the old lease time to something pretty short, maybe 10 minutes, and make sure all of the devices get that new lease time before removing the old scope. Then when the new scope is created, the devices will get a new address quickly. It's may be better if you can turn off as many DHCP devices as you can before deleting the old scope. - PaulGibson 7 years ago