"supernetting" question

[ke6guj]

as a followup to my router question, I am thinking about extending the 192.168.2.0/24 to a 192.168.2.0/23 network. That would give me 512 possible IP addresses. I'm not actually going to be using that many but that would let me keep clean IP address assignments, servers from 192.168.2.10-20, printers from 2.30-40 and mainly set me set one of my DHCP servers to 192.168.2.100-200 and the other one to 192.168.3.100-200. right now, I have to divide that exising 100 IP address block across both servers, 50 for each, and if one DHCP server is down, we can run out of assignable IP addresses.

I know I could probably set up VLANs and do it that way, but as I mentioned in the other thread, this would need to happen during a short trip to Mexico, and I haven't done any VLAN'ing yet, and wouldn't have much time to troubleshoot this. And I won't be on site all the time to maintain it. It needs to be set and forget for the most part. I think changing to a /23 network might be easier since I will already need to touch any statically set devices and adjust default gateway settings so it won't be much to change the subnet mask at the same time. The rest will just get reprogrammed via DHCP.

[Mute]

No reason not to.

[nick]

That will give you 510 possible addresses. Not to nitpick...

Out of curiosity, any reason you're nickle-and-diming IpP assignments there, rather than just using a Class B? Private IPs are free. And you'll have to modify the existing IP config on the hosts with static IP anyway, if that's you concern.

[the86d]

That will give you 510 possible addresses. Not to nitpick...

Out of curiosity, any reason you're nickle-and-diming IpP assignments there, rather than just using a Class B? Private IPs are free. And you'll have to modify the existing IP config on the hosts with static IP anyway, if that's you concern.

That sounds better. 192.168.x.y with a subnet of 255.255.0.0.
Well if you are going to throw them all on the same network anyway, just use a /16 as suggested (or even a 10.x.y.z/8).

[ke6guj]

That will give you 510 possible addresses. Not to nitpick...

Out of curiosity, any reason you're nickle-and-diming IpP assignments there, rather than just using a Class B? Private IPs are free. And you'll have to modify the existing IP config on the hosts with static IP anyway, if that's you concern.

yes, that would be an option, but I'm trying to make this as painless as possible. As it is, I'll need to make minor changes to those static hosts, but if I completely give them new IP addresses, I also have to modify every single static mapping to those devices, such as PBX-PBX connections, printer mappings on local and remote print servers, etc.

By just extending the existing network to include 192.168.3.x, I don't have to change the IP address of existing devices and find every single place where an item wants to connect to that device via its original IP address. I just need to touch the device to update the subnet mask and it is done. I don't have to worry that there are 32 clients that have to have their programming updated to reflect the new IP address.

and yes, on new facility build outs, I am using Class B addressing, but this is an old facility that I can't just go start over. I'm afraid that even just supernetting the existing network is going to be a pain with the short time I'll be on site.

[ke6guj]

That sounds better. 192.168.x.y with a subnet of 255.255.0.0.

can't do that, have to work around other existing networks that we have. I already have other networks at 192.168.10.x, 192.168.20.x, 192.168.30.x. I used to have a 192.168.1.x network that has gone away, which is why this one is 2.x. I could extend the 2.x network to be a /21 or /22 without affecting the other networks, but I can't really see the need to go past the /23 I'm planning on.

[nick]

Well, then it sounds like you got it all figured out anyway

If you have any questions while you're out there, feel free to give me a call. I'm out of the country, but my phone works.

[nick]

And I'd still extend it to /21 or /22, just to reserve the contiguous space. If you have remote access to that site, preconfigure everything you can, so you don't run out of time, should you encounter problems. Checklists are also good

[noob_tube]

Have you considered switching to Class B with a /24?

[jmlivingston]

Setting up vlan's will not help with your DHCP server availability concerns, except that if one server fails it will reduce the number of your clients that are affected by it. If you go too big on the subnets then you're going to pay for it later the next time you re-architect. I'd suggest going no bigger than a /23, but you may want to split it into (2) /24's if you have internal routing capabilities. Set one up for servers and print resources then the other for your clients.

[ke6guj]

didn't get a chance to work on this the last trip down. Am having the onsite tech work on cleaning up old and unused static IP addresses and figuring out if we can keep within the /24 or going with the /23 will be required.

[Jason95357]

To correct what someone else was saying: DHCP servers don't have to be on the VLAN which they service. Any decide non-SOHO router can forward the bootp/dhcp packets to your DHCP servers where ever they are located.

It doesn't apply to your proposed scenario of going from a /24 to a /23, but I don't think they understood things clearly and that you were not planning to introduce VLANs.

If things are DHCP, then changing the mask on all the clients is easy peasy. I would suggest changing all static hosts to DHCP reservation as well, which makes changing the mask, DNS, NTP, and domain name easy to change should you need to. Further, I would move to using DNS for any access, and then you could easily change printers, servers, etc. access just by modifying their DHCP reservation and DNS record. Clients will learn it the next time they look up the DNS record.

Oh, and going from a /24 to a /23 is not a supernet or supernetting. It's just moving from a "Class C" to a CIDR (the first "c" there is for classless, that is, not subnetting on the class boundaries).

A supernet is a group of multiple subnets. If you had two /24 VLANs that you created a route summary statement of /23, that would be a supernet.