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Running out of Ip Addresses

Posted on 2006-04-17
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Last Modified: 2012-01-14
I am currently running out of available IP Addresses.
I have 2 DHCP servers, 1 set to hand out 20 % of the addresses and the other hands out 80% of the addresses.
I know I can set up a relay server, and segment parts of my network,  but I would rather not buy any more additional equipment.

If I set up a superscope,  add my 10.0.0.0 subnet to it, and then add a new 10.0.1.0 subnet to the superscope, will clients that get a 10.0.1.0 address be able to use devices that are on the 10.0.0.0 subnet?

Thanks,

-RBunn
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Question by:rbunn
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LVL 3

Expert Comment

by:hfern
ID: 16472655
Please give a bit more information:
- how many subnets do you currently have
- type of subnets
- number of devices per subnet
- number of routers and switches
This will help us to properly advice you. Thanks.
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Author Comment

by:rbunn
ID: 16472712
I have one subnet right now 10.0.0.0
there are around 230 devices,  but that is going to increase very shortly
1 T1 Router
about 9 swtiches,  
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by:dlongan
ID: 16472778
What subnet mask are you currently using?

For example if you are using a class c (255.255.255.0) subnet mask you are only able to have 254 ip addresses.  But you can change it to a class b (255.255.0.0) really open up your ip range (65,534).

But you may want to partition or (subnet) the network using routers for ease of administration, performance, and troubleshooting.

FYI, You will need to update ANY device that has a static IP address with the new subnet mask also...
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by:Craig_200X
ID: 16472804
if you use a subnet mask of

255.255.254.0 - 510 hosts
255.255.252.0 - 1022 hosts


or if your switches are capable of vlan routing.. use vlans.
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by:Craig_200X
ID: 16472825
note Dlongan s FYI if you change subnets masks....
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Author Comment

by:rbunn
ID: 16472828
It is set up as 255.0.0.0 right now,
Can I just change this to 255.255.0.0 and then update my static Devices?
It cant be that easy....
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by:hfern
ID: 16472896
It is that easy, but there are of course downsides...
I'll just mention2:
1.  if you put all your devices in the same subnet then you will have a lot of broadcast traffic. This will affect your network performance, esp if you have timing critical applications like VoIP in your network
2. maintainability decreases. If you have somewhere a problem in your network then it may affect your complete network, whereas if you split up your network in mulitple subnets, you're more likely top have just in a subnet.
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by:Craig_200X
ID: 16473191
if you have alot of broadcast traffic you will notice performace decrease which case you will want to segment either with vlans or another router.
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Expert Comment

by:mikeleebrla
ID: 16473355
if you are currently on a 255.0.0.0 subnet, that means that you have 16,777,214 usable IPs.  Can you please explain why you think you are running out of IPs since you only have 230 IPs in use with over 16 million available to you????
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by:Steve Knight
ID: 16473438
I suggest you setup one server to give out

10.0.2.1 to 10.0.3.254

and the other

10.0.4.1 to 10.0.5.254

and then disable your existing scopes

Then you have two completely redundant sets of 512 DHCP addresses available from your two servers and next time users get an address they will get one of the new ones.  Use the original 10.0.0.x range for your fixed IP items like servers, routers etc.

Steve
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Expert Comment

by:rsivanandan
ID: 16473587
Looks like we are awfully out off topic here? Running out of ip address doesn't seem to be the case?

Cheers,
Rajesh
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Expert Comment

by:Steve Knight
ID: 16473683
Depends upon your point of view. As far as the network is concerned it has as much expansion potential as anyone could feasibly want but the user perception of course is that there are no addresses because the DHCP scopes are too small and possibly the lease times long so even a brief visit from a laptop user might be using up an address etc...

Anyway I think there are enough answers above that the questioner should be able to decide where to start at least.
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Expert Comment

by:scrathcyboy
ID: 16474364
" will clients that get a 10.0.1.0 address be able to use devices that are on the 10.0.0.0 subnet?"

No, generally NO, unless you provide some way for them to see across the class C domain barrier.
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pseudocyber earned 2000 total points
ID: 16476834
>>It is set up as 255.0.0.0 right now,
Can I just change this to 255.255.0.0 and then update my static Devices?
It cant be that easy....

>>If I set up a superscope,  add my 10.0.0.0 subnet to it, and then add a new 10.0.1.0 subnet to the superscope, will clients that get a 10.0.1.0 address be able to use devices that are on the 10.0.0.0 subnet?

It doesn't seem that you understand what the subnet mask does.

First of all, a "10" network is a private IP range with a "natural mask" of 255.0.0.0 also called /8.  Meaning there are 8 bits in the mask.  Naturally, this network provides you with 2^24 host addresses - 16,777,216 (minus 2 of course).  So if you're running out of 16million plus addresses, you've got bigger problems ...

I'm going to assume you've THINK you've "subnetted" your 10 network down - to around a /24 network - which some people call a "Class C".  Note, with Classless Inter Domain Networking (CIDR) or subnetting, the "classful notation" is kind of old hat and disfavored.

Anyway, you're probably using a mask of 255.255.255.0 on your network, and I'm going to assume the network is 10.0.0.0/24 and your first host is 10.0.0.1 and your last is 10.0.0.254.

NOTE - however, with a 255.0.0.0 mask, you have NOT subnetted.

Now, if you DO decide to subnet, then part of your network will be 10.0.0.0/8 and another part will be 10.0.1.0/24.  

The problem with this is that the /8 network is a "supernet" if you will of the smaller network, the /24.

This means that part of your network will foward at layer 2, and part will think it has to route at layer 3.  This will cause a lot of communication problems and won't work.

SOLUTION:

Instead, give your self more addresses and fix your subnet address all at the same time.  Change all your network devices, using DHCP and static assignments, to a mask of 255.255.254.0.  This will give you 510 addresses and make your 10 network assignment more sensical.

Hope this helps.

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Expert Comment

by:Craig_200X
ID: 16479762
Good job Pseudocyber!


[this was also my solution. but you deserve the points for that great explanation!]
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