Changing subnet mask

[abhijitm00]

Hi All,

As the number of users in our network has increased we need to change the subnet mask for our internal network (205.232.212.X). I have inherited this network and don't know why this address was used but I am trying to figure out a temporary solution till we move to a private IP address.

The problem is we would like to change the subnet mask from 255.255.255.0 to 255.255.254.0 for now to accomodate more hosts. I do not want to change the numbering right now as there would be a lot of work involved for a one man IT dept. DHCP server is a Win2K server.

I just wanted to confirm if the steps that I have outlined are correct. It is a one segment network:

1. Deactivate and delete old scope.
2. Create new scope with changed subnet mask
3. Change subnet masks assigned to fixed IP's - servers, printers etc.
4. Reboot the clients (98/NT/2000/XP)

Do I need to delete the leases for the old scope as well before I begin?

All help is appreciated

 

[minxca]

Why do you want to change the SM and not to Private IP now? It needs the same steps.

 

[criticalUpdate]

what type of router and servers do you have?

Here's an idea that I have implemented in a few places, there could be caveats though... but consider.

using a private net like winoto suggests and creating a dual-mode (only temporarily) on 2 ip networks network. like so....

172.16.x.x 255.255.0.0 is a good example. If you had say a cisco router as a gateway for your internet all you need to do is add a secondary ip address to the interface that is the workstation and servers default gateway say 172.16.0.1 with sm 255.255.0.0

Then if you server were say w2k just add a secondary ip address on that connection for 172.16.0.10 or whatever address in the 172.16.x.x that you would like.

Now all you need to do is decommision the above scope and add one for the 172.16.x.x net.

as long as the router routes back and forth from the 172.16.x.x network to the 205.x.x.x net then your ip traffic is happy and since the server is responding on both nets broadcasts that don't normally get forwarded by the router are usally happy.

let the scope take place as the leases time out and reconfig the other devices at your leisure.

Pluses are as follows

the network can be slowly migrated to a normal ip private class C, B or A.

you should now be able to reach address in the public world that normally respond to the 205.232.212.x ip's which are probably unreachable right now because they would resolve locally.

instead of sneaking up 1 bit on the bitmask you would have a whole class b range or class a if you'd prefer.

a bit long winded of a scenario but I hope it's helpful.





Jeff

 

[abhijitm00]

Thanks Jeff for the up date. I just did what you mentioned yesterday and we moved to a private IP address 192.168.X.X and everything is working fine. Thanks for the tip.

 

[criticalUpdate]

wow you work quick!

Jeff