How to change netmask and ip to get more DHCP addresses

luke240778 · Nov 30, 2011, 7:38 PM

Can someone please tell me how i can make my OPT1 interface DHCP for up to say 10000 clients?

I am not sure what is best to change the netmask to and also what ip range is ok to use.

should i use 255.0.0.0 or 255.255.0.0 ?

with IP should i stick with 192.168.100.0 or should i use 192.0.0.0 ?

I dont really understand all this very much. i just need to know how to have a dhcp pool of up to 10000 IP's.

Thanks in advance

dhatz · Nov 30, 2011, 8:26 PM

You can't use 192.0.0.0 (since the relevant private IPv4 address space is 192.168.0.0/16 i.e. 192.168.0.0 – 192.168.255.255)

You could use a /18 netmask for a total of 16K IPv4 addresses.

luke240778 · Nov 30, 2011, 8:29 PM

Strangely i tried that first, but i got some strange result.

I made my interface IP: 192.168.100.1 / 18

Then when i went to the DHCP server to change the range, it was saying the IP was 192.168.64.0

So that made me think i was doing something wrong.. 16k is fine by me

Nachtfalke · Nov 30, 2011, 8:42 PM

/18 means you can use

192.168.0.0/18 - 192.168.63.255.255/18 16k IPs
or
192.168.64.0/18 - 192.168.127.255.255/18 16k IPs
or
192.168.128.0/18 - 192.168.191.255.255/18 16k IPs
or
192.168.192.0/18 - 192.168.63.255.255/18 16k IPs

dhatz · Nov 30, 2011, 9:00 PM

Since you had configured your interface IP as 192.168.100.1 the system picked the correct range for you 192.168.64.1 - 192.168.127.254 which would correspond to a /18 netmask that would include that IP.

luke240778 · Nov 30, 2011, 11:24 PM

Ok i see.. so i could still start my IP pools from 192.168.100.1 if i wanted to right? seeing i am not going to need all 16k ip's

Nachtfalke · Nov 30, 2011, 11:45 PM

If you are starting at 192.168.100.1 as DHCP pool instead of 192.168.64.1 than you just have ~7100 IPs in your pool.

192.168.100.1 - 192.168.127.255.255 ~ 7100 IPs

luke240778 · Dec 1, 2011, 5:01 AM

perfect. I'm only going to need somewhere between 5000 and 7000 anyways.

Nachtfalke · Dec 1, 2011, 4:18 PM

@luke240778:

perfect. I'm only going to need somewhere between 5000 and 7000 anyways.

In theory you then can use a /19 Netmask. This is enough for 8.192 Users.

192.168.0.0 - 192.168.31.255 8.192 IPs
192.168.32.0 - 192.168.63.255 8.192 IPs
192.168.64.0 - 192.168.95.255 8.192 IPs
192.168.96.0 - 192.168.127.255 8.192 IPs
192.168.128.0 - 192.168.159.255 8.192 IPs
192.168.160.0 - 192.168.191.255 8.192 IPs
192.168.192.0 - 192.168.223.255 8.192 IPs
192.168.224.0 - 192.168.255.255 8.192 IPs