[Dnsmasq-discuss] I want to try and set up a DHCP "server" to handle one subnet

[Matt Ginzton]

>> How to restrict my server's DHCP offerings to a single subnet.
>> 
>> How must the Other DHCP server and routers be modified to permit this.
>> ?? Disable DHCP relay to/from this subnet ??
> 
> That's it. DHCP won't go outside a "broadcast domain" without a DHCP
> relay, so if the main DHCP server is on another subnet, then there must
> be a DHCP relay. Stop that and there will be no DHCP service from the
> main DHCP server on your subnet.

Don't you want to distinguish between subnet (layer 3 concept) and segment
(layer 2 concept) here? There may be people who've set up multiple subnets
just by IP addressing, on the same L2 ethernet segment, and at this point
assuming there's no DHCP interference would be dangerous.

Assuming ethernet, it's the L2 concept (ethernet segment) that will determine
the broadcast domain.

Basically, make sure your different subnets are also on different ethernet
segments, then the broadcast domains will be separate and DHCP will be
separate as you'd expect.

Matt