Subnetting Advice please.

[bigkeith]

Hello all,
Our internal network has a rather limiting ip range of 1.1.1.0 with a subnet of 255.255.255.0 As our company continues to grow we are struggling to manage with the limited number of IP addresses that this gives us. I am planning to change our subnet to 255.255.0.0, giving us plenty more IP addresses for expansion. As I see this, the 255.255.255.0 devices will fail to see new subnetted devices. If everything goes well, and we plan the order in which we subnet devices, then it should be a fairly straightforward task. Am I right in this assumption? Once we start the process then the rollercoaster ride starts, as I think we'll have to complete the changeover to eliminate any problems. If anyone has any experience of performing a similar task then I'd appreciate any help before we start - pitfalls, problems etc as I might be way off the mark.

Incidentally, I'm leaving the rather unconventional ip range as I feel it'll have less of an impact on the project as at least the new subnet should still see all of the network, but I'm up for persuading otherwise should the general concensus prove otherwise.

Many thanks in advance

Keith

 

[burtsbees]

It really depends on the routing protocol(s) in place, if any, especially if it uses auto-summarization---that can really screw things up. What kind of routers? Are there VLANs in place?

Burt

 

[kmills]

Keith,
Not knowing what all you have on your network, I can only offer what we learned with a network consisting of DHCP servers, mix of static & reserved & DHCP-enabled IP addresses, switches, routers, PCs, VMS boxes, printers, etc.

Train users to do ipconfig/renew. Have everything turned off before you start. Reconfigure DHCP. Configure switches/routers with IP helpers. Turn on DHCP server. Manually reset all static IP addresses. Add new routes to anything needing routes. Work from most remote to closest.

Plan on it taking twice as long as you planned!

It is worth it, good luck.

Kmills

 

[LawnBoy]

As I see this, the 255.255.255.0 devices will fail to see new subnetted devices.

Correct. The new subnet will see the old, but not vice-versa.

This should be fairly painless, but you're right that once you start, you have to finish (for everybody to see everything). Burtsbees has a good point, any routers or VLANS will also need to be accounted for.

 

[picohat]

I think you can also create other subnet, like 10.1.1.0/255.255.0.0 to expand as new network if possible, as long as you configure routing correctly on company router. This way is only work if you want to use private IP range..

If not, you might need to plan very well before converting to 255.255.0.0 especially if you have lot of PCs/servers on 1.1.1.0 network.

Hope helps..




picoHat
Home Network, Wireless Network and Computer Networking Made Easy

 

[bigkeith]

Many thanks to everyone who posted advice and observations on my query. We do route between two internal networks via a layer 3 switch, which I have taken account of. I'm planning the changeover this weekend, and for some reason I'm not allowed the following week as holiday

Much appreciated.

Keith

 

[gb0mb]

Kmills,

isn't this an infinite loop that prevents you from executing your plans.

"Plan on it taking twice as long as you planned! "

Just a little Friday humor.

Gb0mb

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