Running Out of IP Addresses

Posted on 2016-10-04
Last Modified: 2016-10-10
      We are running out of IP addresses on our LAN. The scope is - Between static IPs, Reserved IPs and all the mobile devices we are constantly bumping up against the limit. How can I increase the quantity of IP addresses available?
Question by:daskas27
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Expert Comment

by:Darth Vader
ID: 41828024
changing your subnetmask can change things or even better use VLAN if possible to manage logical groups.
Modify DHCP, layer 3 switches and routers + firewall, and maybe proxy.
LVL 24

Expert Comment

by:Brian B
ID: 41828061
Perhaps introduce a second DHCP range for the wireless devices? You'll just have to use some routing to allow them to get back to the original range.
LVL 96

Accepted Solution

Lee W, MVP earned 500 total points
ID: 41828128
I agree with adding a VLAN but you will need to put in routes for it.  

The alternative as Darth Vader recommends, is to change the subnet mask from to - this will give you to as usable addresses (that's essentially doubling the number you have).  But EVERYTHING must have it's subnet mask changed or they can have problems communicating.
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Expert Comment

ID: 41828909
Just some general things, what is your DHCP lease time?  How about setting it to 24 hours?

Do you clear out reservations for defunct equipment regularly?

The guys above are correct but my suggestions can be useful practice.

Expert Comment

by:Kimberley from Paessler
ID: 41829381
Is there a reason you're limiting yourself to the range -   There are lots more private IP addresses available, which you can use (as long as these ranges aren't already in use somewhere else in your company):
  • -
  • -
  • -

If you're not the person responsible for assigning IP ranges in your company, then ask the person who is if you can have an additional range to use.  The easiest (most optimal) additional range for you would be to, as LeeW mentioned above.
LVL 24

Expert Comment

by:Brian B
ID: 41829862
Actually, just to add to the list of possibilities, it is a good idea to have your static IPs (servers?) in a separate range than your dynamic IPs anyway. So if you move your dynamic IPs to a new range, you can assign it the full range and get even more IPs that way.

Author Comment

ID: 41831691
I like the sound of Lee's suggestion "change the subnet mask from to - this will give you to as usable addresses (that's essentially doubling the number you have).  But EVERYTHING must have it's subnet mask changed or they can have problems communicating." But am a little concerned with "Changing EVERYTHING" to the new subnet mask.
LVL 96

Expert Comment

by:Lee W, MVP
ID: 41831718
Ok.  Care to elaborate?  

If you don't understand networking, I'd suggest hiring a professional to do it for you.  If you change the mask, then only devices with the same mask can communicate!

Your only other option is to add a new logical network and a router between the two of them.
LVL 24

Expert Comment

by:Brian B
ID: 41832012
But am a little concerned with "Changing EVERYTHING" to the new subnet mask
I suspect a lot of your device are getting their address from DHCP? So changing the subnet mask the the DHCP server hands out will look after a lot of things.

If you wish, Experts Exchange offers the ability to hire an Expert to help you with things like this. This could either be a Gig (short term project) or may even be a candidate for Live Help.

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