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poconnor
Asked: 2012-03-07 07:05:20 +0800 CST

What can I do if my organization is running out of IP addresses?

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My organization is going to run out of local network IP addresses within the next few months. We are expanding to get a ton of new people and we are switching over to Lync IP phones.

Crunching through the numbers, we have about 253 addresses on the network and we are going to have over 300 IP devices. I'm not sure what I should look into to fix this problem.

I'm the server administrator, but I don't have a background in networking. I tried setting my computer from 192.168.1.XXX to 192.168.2.XXX, but it complained about a subnet issue. I left all the other settings the same as they were; subnet, DNS, gateway.

I just need to bring this up to my manager, with a couple ideas on how to fix this. Then maybe we can consult outside help if it will be to over my head. But in the meantimes I just need some ideas.

router networking ip gateway

3 Answers

  1. You were on the right track - use the full 192.168.0.0/16 subnet and you'll have access to plenty of ip addresses (64k).

    You'll need to expand your DHCP server to publish these addresses and possibly change your netmask to 16 (255.255.0.0) rather than 24 (255.255.255.0)

    http://jodies.de/ipcalc?host=192.168.0.1&mask1=16&mask2=

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  2. Is this an Windows environment? If so, the subnet issue is resolved by adding this into Sites and Services and modifying the DHCP scope to include the 2nd range.

    Might be a good idea now, to separate your LYNC IP phones to a separate subnet or even better completely different VLAN on the switches. Having this on a different VLAN will give you better QOS control and easier to troubleshoot when you have networking issues.

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  3. *I tried setting my computer from 192.168.1.XXX to 192.168.2.XXX, but it complained about a subnet issue. I left all the other settings the same as they were; subnet, DNS, gateway."

    That's probably why it complained. If you have a 255.255.255.0 netmask (or a /24, pretty normal default for a 192.168.x.x IP), your host is 192.168.2.x and your default gateway is 192.168.1.x, the default gateway is no longer reachable.

    There are a couple of ways of doing this, the first thing you wnat to do is to sit down and think about your probable addressing needs for the near and medium future (up to a ~2 year horizon is probably a good estimate for the planning you should do).

    You'll need to make an address plan that gives enough IPs for your needs. YOu probably want to split this down into "servers", "workstation", "IP telephony" and "infrastructure management" (to the extent that makes sense). Allocate subnets that are large enough for your needs, but still small enough to not cause broadcast performance issues. I don't know how noisy Windows is on broadcast, these days, but it used to be that you didn't want more larger than about a /23 (~500 machines) in a single netblock.

    You may also want to further sub-divide your network ranges by geographic location (floors, buildings).

    The reason why you wnat to plan for at least a bit of future expansion is that renumbering is time-consuming (less so if you use DHCP, though), there's at least some configuration to be done (firewalls, access lists, router interface configurations, ...)

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