DHCP range limit

Network DHCP
1

Hi,

The online doc explains that the range “must fit into a /24 net” (mask).

But then at the bottom of the page there is an example of a range 10.1.0.1 to 10.1.255.254, waaayyy beyond /24. Yes it is an optional dhcp.conf.local, but why declare this exactly as the dhcp.conf for #GREEN ? Confusing…

I’m looking to implement a range in a /23 network, like 192.168.0.21 to 192.168.1.250. Is this possible, and how?

Thanks,

Michel

2

Hello Michel,

yes, it is of course possible to use subnets that are not /24. There are no limitations on the DHCP range whatsoever, it just has to fit into your subnet of course.

So, just configure your subnet as usual during setup and then pick any DHCP range.

3

and you have to make sure that your subnets do not overlap and that is easier to identify for many people when using a /24 subnet, which is probably why many use it.

4

The wiki states the fitting based on the example.
The netmask of it is 255.255.255.0 or /24. If you defined your network as /23 ( netmask 255.255.254 ) the check is made for this network.
Your example uses a GREEN network 192.168.0.0/23. This mean all IPs 192.168.0.1 … 192.168.1.254 are allowed.

The example at the bottom of the page uses a very big GREEN net (10.0.0.0, netmask255.0.0.0).

EDIT: I have updated the wiki.

5

Hello everybody, thanks for the clarification.

But this morning at 07:30 the wiki still said the next: “With the current implementation this range must fit into a /24 net (netmask 255.255.255.0).” I’ve spent 3 hours checking the internet on ISC DHCP what could impose that limit. Because a ‘current implementation’ to many people means the current version of IPFire!

Thanks Bernhard to update the page, much clearer now.

6

@mickey6
BTW: welcome to the IPFire community.