Running out of IP addresses

5 pts.
Tags:
DHCP
DNS
IPv4
Networking
Networking services
We've been using 192.120.197.x with a subnet mask of 255.255.255.0 for our network for years. Due to adding more and more systems, we're quickly running out of available addresses. What is the easiest way to get more address? Can we simply change the subnet to 255.255.0.0 on all our devices? Thanks, David

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You could do that.. If you would like take a look and run the numbers from this subnet mask calculator. http://www.cotse.com/networkcalculator.html put in the amount of hosts you think you will need and it will give you a mask that will work for you. If you are honestly getting that big I would recommend segmenting the system with a router and vlan switch. it will be easier to manage and trouble shoot down the road and probably more efficient.

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  • Larrythethird
    Unless you work at HP, you should change the numbers to 192.168.x.y. The 192.120.197.x numbers are owned by HP. Run whois 192.120.197.1 and you can see this. This will cause you some trouble if you are directly connected to the internet. You can use 192.168.x.y with a subnet mask of 255.255.0.0 and have an internal class B network. Of course, these are also not internet routable. I would assume you are NATing to get outside. If so, the internal numbers do not really matter.
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  • Dfng2002
    I concur, break up your sections into VLAN's and posible use other private IP's 172.xxx.xxx.xxx or such into seperate sections through a router, too many company's are relying on switches to do everything for them, while quite useful, having too many can cause network problems.
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  • Spadasoe
    I agree with both of the previos. You should really switch to private addresse on the inside. Sinc you need more than 256, I would suggest 10.x.x.x. This gives you more flexibility, you can create nice well defined subnets, easier to define acls for routers and pix, and personally, looking at lots of numbers all day, 10.x.x.x to me is easier on the eyes that either 192 or 172 networks.
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  • Studio90
    If this is a private IP range, I would suggest changing it to the 192.168.x.x or 172.x.x.x range like the folks before me. If you don't you may eventually have issues with Internet traffic. After that, I would suggest supernetting a Class C range by using a 255.255.252.0 subnet mask. That should more than cover you for right now. If this is public address range (?!), add NAT to your firewall and see above. - S.
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  • Mousejn
    The list of private IP addresses that are not used on the Internet are: 10.0.0.0 - 10.255.255.255 172.16.0.0 - 172.31.255.255 192.168.0.0 - 192.168.255.255 If you need more than 254 addesses you can change the subnet. 255.255.254.0 that gives you 510 ip addresses.
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  • Padapa
    All the previous replies are right on. You can't just change the mask. Moving from a 255.255.255.0 to 255.255.0.0 would move you from 254 devices to 65,534 ... All in HP's space. You can use multiple Class C address groups and seperate your traffic. An example would be? 192.168.100.xxx for computers and servers 192.168.101.xxx for VoIP phone services Make sure your ethernet switches are up to date and it works fine and allows you to keep traffic loads managed for delay sensitive traffic types. Are all you devices used at the same location? If not, separting each location into it's own class C address space work very nicely as well. Good luck and I would move off HP's private address space asap. Check out Wild Packets Free subnet calculator.
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  • sabiodun
    I WANT TO ASSUME THAT YOU ARE USING PRIVATE IP ADDRESSING, IN THAT CASE LOOK AT YOUR ANTICIPATED GROWTH PATTERN FOR THE FUTURE AND SCALE ACCORDINGLY. IF YOU BELIEVE YOU WILL GROW VERY BIG WHY NOT IMPLEMENT A CLASS A ADDRESS SCHEME THIS SHOULD GIVE YOU "UNLIMITED" NUMBERS OF IPS. ELSE, GET YOUR SELF A ROUTER AND BREAK UP THE NETWORK. RGDS aBIODUN
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  • petkoa
    Hi David, May be I'm slightly out of topic - this is because pevious posters covered almost every aspect the increasing of IP space per se - but I have a suggestion about the technical procedure. If you are running out of class C address space, almost certainly you have implemented a DHCP server. I'd suggest when you decided on the future addressing scheme, ways of NATting, etc., decrease in advance the lease time of the DHCP-assigned IPs to something like 30 min or less; "in advance" should be about twice the current lease time. Then, at convenient time (may be after work hours), change the configuration of the IP space and return back to normal lease time. This will increase somewhat the unproductive load on your LAN, but will save a lot of calls from angry users... BR, Petko
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  • DKoch67
    Thanks for all the good comments. I was unaware that 192.120.x.x was HP's, but we only use it internally behind NAT (at our single location). I inherited the scheme, but am not against changing to 192.168.x.x. David
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  • Devang
    hi david here u can use the class B ip private IP address range and use the appropriate subnat mask by calculating number of host require this will help you out in further expansion and other thing you can do is u can use the class C address with the different subnet. thanking you Devang G. Patel Sr. Network Engineer GMS
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  • Paul144hart
    Easiest way out is to add a subnet, e.g., 192.120.198.x. Its a bit risky because you risk routing outside your NAT'ed area. The routers, switches should be able to have more than one subnet (classless routing). Creating a VLAN, and physically separating the nets would help in avoiding congestion.
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