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Increeasing available IP addresses

Pkafkas
Pkafkas asked
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Last Modified: 2010-03-18
Hello:

We are interested in having more IP addresses available to us on our network. We currently have an IP scheme of:

IP Address:         192.168.1.1 - to 192.168.1.255
Subnet Mask:      255.255.255.0
Default Gateway: 192.168.1.1

Total of 255 hosts and we are interested in changing this to:

IP Ranges = 192.168.0.1 - 192.168.7.254
Subnet Mask = 255.255.248.0

192.168.0.0 = Network Address.
192.168.7.255 = Broadcast Address.

Total  of 2,046 hosts.

My question is what do we have to do to begin implementing this scheme on our Network?  By the way, we have a Static IP addres scheme for now.  This is the netowrk I was inherited.  I eventually would liek to go to DHCP; but, we must have more available IP addresses first.

1.  Do I just need to change all of the Subnet Mask addresses to 255.255.255.248?

2.  Or do we have to change the Default Gateway to 192.168.0.1 and/or anything else?
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Top Expert 2010

Commented:
you do not have the change the default gateway unless the IP address of the default gateway changes.  if the IP address of the default gateway shifts, then all devices that have the gateway specified will have to be changed to match the new IP of the gateway.
Steve KnightIT Consultancy
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Commented:
Exactly.  Just change the subnet mask.  Until you start using addresses outside of the range already used everything will be able to talk to each other anyway.  Only once you use an address outside the original range will it try and go to it's default gateway rather than direct and fail.  Don't forget print servers, phone devices, switch management settings etc. of course.

Commented:
Hi,

It should be pretty simple, but it will take a little time and effort to fix this all up.

If you haven't already, do a little planning on where you want everything in the address space.  It's optional, but the folks that plan and organize their network do something like:
1-10 Routers
11-50 Servers
51-100 Static
101-200 DHCP (or workstations if no dhcp)
201-250 VPN Connections
251-254 Special/Reserved

When you are ready to begin, go around to all of your routers, servers, and other network devices such as printers and change the network mask.
If you wish, set up a DHCP server (on one of your servers, a router, whatever... I'd recommend using a server).  Make sure that you don't have the DHCP server passing out address that are already assigned statically (manually), or that you plan to have statically (manually).
Go around to the rest of the machines (PCs or whatever...) and either expand the network mask, or just switch them to DHCP/Automatic if you set up your DHCP server.

Most importantly, don't rush through this.  Take your time, do some testing as you go to make sure things are going okay, and allow some time to for a problem to show up and get reported to you before you switch everything over and find that no one can work.

I'd expect to do this a little at a time over the course of about a week, but once done, especially with DHCP, you'll enjoy it much better.

Hope this helps,
Alan
>1.  Do I just need to change all of the Subnet Mask addresses to 255.255.255.248?
255.255.248.0, and yes.
>2.  Or do we have to change the Default Gateway to 192.168.0.1 and/or anything else?
Just the default gateway, yes.

But don't forget these settings need to be changed on ALL machines.
PkafkasNetwork Engineer

Author

Commented:
I'll try it out.  I will see if a new pc will work with the following settimgs:
192.168.0.25
255.255.248.0
192.168.1.1

Aditionally, I think there are a couple of Ethernet switches that still have the old subnet mask;l but, theat should bnot make a difference, correct?
IT Consultancy
CERTIFIED EXPERT
Commented:
The subnet mask on anything other than a core switch (which is doing routing etc.) makes very little difference, it is typically only for management purposes (i.e. you need to change it but it won't stop it working).

Steve

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