IP Address redesign

Wyandotte
Wyandotte used Ask the Experts™
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We currently have a network of 192.168.0.0/23 which gives us 192.168.0.1-192.168.1.254. We have another remote location through site to site vpn that uses 192.168.3.0/24 and a 3rd site to site that uses 192.168.4.0/24. We are running out of IPs and trying to decide what is best. We are considering setting up a vlan for each department and giving them their own block of IPs. We are considering supernetting the 192.168 network for all departments. Each department would have 512 addresses. 192.168.0.0/23 for one, 192.168.2.0/23 for another, 192.168.4.0/23, 192.168.6.0/23 etc. Are there any potential problems with doing this? Is it better to subnet a class a or b using 10.0.0.0 or 172.16.0.0 or will it not matter. It will be substantially easier to stay with 192.168.0.0/23 due to the fact that much less will need changed in order to do that.

I am trying to come up with a plan that is best for the next 30 years and that will be easiest to implement. Any ideas?
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The 512-address per department is a sound design - as long as you know you'll never exceed those seat numbers. When you say you're 'running out of IPs' I take that to mean that your /24 locations are getting bigger, since you'd like to stay at the /23 for your main location.
If you'd like to future-proof yourself a bit, put some space in between your location IP assignments. Like this:

192.168.0.0/23
192.168.10.0/23
192.168.20.0/23

This way, you could greatly expand these segments at a future date without bumping into the network boundary of the other locations. Just a thought.

As far as what class you use, it doesn't matter in the private space.

Author

Commented:
I am running out of space at all locations and I don't think I should go over 512 hosts per vlan. I could leave the data center at 192.168.0.0/23 and that will be enough addresses for this building for quite some time. There are only about 70 being used right now. I could then open up the remote site that is 192.168.3.0/24 to include the .2.0 which will double their IPs and then give them several subnets after that for room to grow. What is the maximum number of hosts per network. We don't need to vlan for security, I just thought I shouldn't go over 512 hosts per network. Am I wrong in thinking that?
Back in the day, flat networks were terrible just because of the chattiness of broadcast traffic due to DHCP, etc.. Is it that much of a dealbreaker today? Most likely not, but your 512-host limit is still a good practice.
I like your idea of enveloping the .2 into your .3. That's what I did the last time I had to redesign at a shop.
Lots of opinions out there...
https://learningnetwork.cisco.com/thread/10668
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Author

Commented:
I read that thread when I was google searching the topic. I wanted to get an opinion on here. I think we will go that route. thanks.
Aaron TomoskyDirector of Solutions Consulting

Commented:
Another suggestion: if your users ever VPN, it can cause issues if you use 192.168.0 or .1 as most all consumer routers are default to 192.168.0.1 or 192.168.1.1. I'd either stay off those two or just move up to 10.

Author

Commented:
We have a Cisco vpn currently with a few dozen users and don't have any problems.
Aaron TomoskyDirector of Solutions Consulting

Commented:
If you have a server at the office with an ip of 192.168.0.101 and your user is at home and their dhcp range starts at 192.168.0.100 and their media server or whatever is at 192.168.0.101 then I think they can't reach your server.

Author

Commented:
Correct, but most home networks start their IPs at 100 and our servers are all below that. Thanks for the tip though.
I would consider breaking it up so that you have actual subnet boundaries.  At least, at times, this simplifies setting up routers, firewalls, etc.

Then you would use:
192.168.0.0/23
192.168.8.0/23
192.168.16.0/23

This way the subnets not only do not overlap but can be increased in size to /21 in some fashion while maintaining the ability to use CIDR notation such as:
And each subnet can be referred to as:
192.168.0.0/21
192.168.8.0/21
192.168.16.0/21

If you choose other boundaries then you can't use this notation to refer to an entire subnet - should you choose to make one larger later on.

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