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IP Addressing Problem

Posted on 2014-10-08
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Last Modified: 2014-10-16
I have an existing network which i have configured it as below.

Servers/AP/Printers/etc
Static IP: 10.10.10.1 - 10.10.10.80
Subnet Mask: 255.255.255.0

Workstations
DHCP IP range: 10.10.10.81 - 10.10.10.253
Subnet Mask: 255.255.255.0

Now, as the company expands, I am running out of IP addresses for new workstations. How do I expand the address range/subnet? I have never faced this kind of environment before.

Thanks.
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Question by:nacha9817
9 Comments
 
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by:Wilder_Admin
ID: 40367989
So like always its depending how you used already. If you use already a router or not.

So what you have to do is to expand your network here you have 2 different possibilities. You can use for your workstations a own subnet like 10.10.11.0 /24 and leave the servers etc in the old subnet. I think is the easiest in ur situation. That can be done in your dhcp server. But think about the dhcp reservations if you use for workstations.

So you have to configure ur router that these two network can reach eachother and the dhcp server.
The clients will still work until they ask for a new lease. until that time you should changed the router already.

Second is a different network for the new clients then you make a new scope on the dhcp server and you route them to the old one.
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Mohammed Khawaja earned 300 total points
ID: 40368014
I suggest you increase your existing subnet by changing from /24 to /23.  This will give you subnet 10.10.10.1 to 10.10.11.254 255.255.254.0, essentially doubling your network.  What you need to do is change the DHCP scope and only other devices/machines that needs changing would be ones that have static addresses.

Putting your servers in a different subnet is not recommended unless you are sure that your router can handle traffic as well as it does not cause extreme slowdown (i.e. if interfaces on your router is 100 mb but all your servers and clients are 1 gb then separating them to 2 subnets will result in clients talking to servers at 100 mb).
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Expert Comment

by:frankhelk
ID: 40368071
I agree with Mohammed Khawaja in priciple.

But since the class A private network address space (the 10.x.x.x) range is defined by the IANA as 10.0.0.0/8 (mean it has a mask of 255.0.0.0) you could even think big ... as long as there are no other networks conflicting in your company environment, just change the address mask at the existing systems to 10.0.0.0/8 and you have approx. 255^3 addresses at your command.

I think expanding the mask by just 1 bit would surely double the address space, but that would bring you to change tha mask again in a couple of months. Wit a change to a full class A net you're as spaciaous as you could be as long as you don't grow up to the size of IMB, Apple or Microsoft ;-)
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Expert Comment

by:dipersp
ID: 40368175
And I would rally AGAINST a full class A only because it could bite you later if you ever need to link up to another network in the 10.x.x.x range.  DO expand your network using Mohammed's recommend, but don't go full hog.  Being as you're already using 10.10.10.x (Which is great, since most no one ever uses that), expand by a few C classes (Maybe 10.10.10.x to 10.10.20.x.)

The biggest part of this job is changing all of the resources that are static off-hours.  But being as you're currently in the same subnet, doesn't mean they all have to be changed at the same exact time.  Just make sure everything has the new subnet before you start using any addresses in the newly expanded range.
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Expert Comment

by:Mohammed Khawaja
ID: 40368204
I agree with Dipersp and I may go as far as using subnet 255.255.252.0 but I would not use the whole A class.  You may need additional networks later on (i.e. test, qa, etc.) and it would be a pain to change the network again.
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Expert Comment

by:Fred Marshall
ID: 40369976
I prefer to not mention "classes".  Just consider what's available and how to partition it in some sensible way.
Maintaining margin for growth is good practice.
Enough said.
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Assisted Solution

by:vivigatt
vivigatt earned 200 total points
ID: 40370385
I suggest that you extend the pool of addresses to a /22 subnet mask (better than a /23).
To avoid disruption, you can, provided that you do not have any node that currently has an IP address in the "new pool" of addresses :
- keep all existing routing devices DNS, DHCP, WINS etc. with their existing IP addresses, just change their subnet mask
- change subnet mask on the static devices but keep their existing IP addresses and router/DNS settings
- delete the existing dhcp scope and create a new one with the new subnet mask. Remember to exclude the static devices from the pool.

Some resources that will help you:

http://www.subnet-calculator.com/
http://support2.microsoft.com/kb/255999
http://technet.microsoft.com/en-us/library/dd145324%28v=ws.10%29.aspx
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Author Closing Comment

by:nacha9817
ID: 40384408
Hi All,

Sorry for the late reply. Thank you all so much for the solutions recommended.  I would go for /23 or /22 subnet. How do i reconfigure my dhcp so that the ip address issue are 10.10.10.x & 10.10.11.x with the subnet mask of 255.255.255.253 ?

Many Thanks & Best Regards
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Author Comment

by:nacha9817
ID: 40384418
Oopss!..Mistake in my "Comment" page. It should be subnet mask of 255.255.254.0 instead of 255.255.255.253
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