1

Our DHCP is running out of addresses. I cannot extend the range and would like to resubnet.

Right now our addresses are:

10.1.24.1-254 255.255.255.0

Would I change the subnet to 255.255.254.0 ?

What would the available addresses be at that point? 10.1.24.1 - 10.1.25.254?

3
  • Well if you add one port bit to the host address, you go from (2^8-2) to (2^9-2) available addresses (510). 10.1.24.0/23 is a valid network address.
    – Zoredache
    Aug 29 '13 at 20:28
  • You say you can't extend the range, but then your question is extending the range...?
    – fukawi2
    Aug 29 '13 at 23:15
  • I did the re subnet and should have 10.1.24.1-10.1.25.254 however, anything with 10.1.25 will not connect to the internet. Only the original 10.1.24.x address will connect. I've changed all the routers and gateways to have the 255.255.254.0 subnet and I can connect to any computer with 24 or 25 in the address. Just can 25 to connect to internet. Any ideas?
    – Damon
    Aug 31 '14 at 22:30
5

Yes, you're right. The range of available addresses is going to be 10.1.24.1 - 10.1.25.254

If you execute ipcalc on linux the output is

# ipcalc 10.1.24.0 255.255.254.0
Address:   10.1.24.0            00001010.00000001.0001100 0.00000000
Netmask:   255.255.254.0 = 23   11111111.11111111.1111111 0.00000000
Wildcard:  0.0.1.255            00000000.00000000.0000000 1.11111111
=>
Network:   10.1.24.0/23         00001010.00000001.0001100 0.00000000
HostMin:   10.1.24.1            00001010.00000001.0001100 0.00000001
HostMax:   10.1.25.254          00001010.00000001.0001100 1.11111110
Broadcast: 10.1.25.255          00001010.00000001.0001100 1.11111111
Hosts/Net: 510                   Class A, Private Internet
6
  • 1
    Upvote for ipcalc. Didn't know that existed. Nifty.
    – Safado
    Aug 29 '13 at 20:29
  • It is a good tool to calculate subnetting ranges and this type of stuff... ;) Aug 29 '13 at 20:33
  • Only problem with ipcalc is...based on the OP's other questions, they are in a Windows environment. :) But the resulting output is the important thing here, not the tool used.
    – TheCleaner
    Aug 29 '13 at 20:45
  • @TheCleaner - it's perl, so theoretically it shouldn't be all that difficult to get it running under windows.
    – EEAA
    Aug 29 '13 at 20:48
  • There are a bazillion tools for this, but I'm partial to this one for Windows: bitcricket.com/ip-subnet-calculator.html
    – joeqwerty
    Aug 29 '13 at 20:51

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