Fredric Robinson
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Proper way to expand available IP addresses using DHCP Server 2008
We have a windows server 2008 with DHCP enabled. The scope properties display [172.22.0.0] with start IP 172.22.1.100, end IP 172.22.1.255, subnet 255.255.0.0. We want to know the easiest way to increase the number of IP addresses (example 1000 max) that can be given out by the DHCP server and make sure that everything is still routeable. For example, if one of the new IP addresses let's say is 172.22.2.x will that device be able to see the server at 172.22.1.4 and access the gateway at 172.22.1.1? We want to know how to do this and set it up properly.
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Soulja
Yes Bryant is right. Just to add. Routing should work fine as you are routing for the entire /16 despite the scope configured for the dhcp server.
While your IP addressing allows for a very large subnet, your DHCP server is actually only offering from a pool of 155 addresses.
There are a lot of things you could do to expand that pool, and which ones make sense will depend on things you don't mention:
Presuming the address space above the current pool is free, all you need to do is change the ending IP from 172.22.1.255 to - as Bryant notes - something like 172.22.4.255 or 172.22.5.255, which would give you something like 960 or 1,175 DHCP IP addresses respectively.
There are a lot of things you could do to expand that pool, and which ones make sense will depend on things you don't mention:
- Are fixed IPs assigned below and above the extant pool?
- If so, can they be re-assigned?
- If so, and they can't be re-assigned, can they be worked around?
Presuming the address space above the current pool is free, all you need to do is change the ending IP from 172.22.1.255 to - as Bryant notes - something like 172.22.4.255 or 172.22.5.255, which would give you something like 960 or 1,175 DHCP IP addresses respectively.
ASKER
Ok, I understand what you are suggesting. Let's assume I expand the scope to end at 172.22.4.255 and a new network printer is installed and gets an IP address of 172.22.3.100 will all devices on 172.22.1.x or 172.22.2.x or 172.22.4.x be able to see it? Are there any limitations on visibility with the new IP range?
Yes, they can see it just fine. The limitation that creeps to mind, is that you now have a broadcast domain that can have literally have 65,534 hosts. Not really a limitation as much as bad design.
Fredric... please understand Paul Mc. recommendation.
You should not have critical devices on a DHCP server. This is an open door for problems even if they connect by DNS.
Any device in a range of 10.10.X.X to 10.10.255.255 with a mask of 255.255.0.0 will be able to see each other if the router/gateway is within this very same range... this is by design!.
You should not have critical devices on a DHCP server. This is an open door for problems even if they connect by DNS.
Any device in a range of 10.10.X.X to 10.10.255.255 with a mask of 255.255.0.0 will be able to see each other if the router/gateway is within this very same range... this is by design!.