isc-dhcp 4.4.2-p1 shared-network confusion

[Simon Hobson]

Philippe Maechler <plcmaechler at gmail.com> wrote:

>> Yes, but ...
>> If (say) the GI-Addr is 20.1.0.1 then ONLY shared-network xyz is a
>candidate. The other subnets and shared-networks are irrelevant as the
>GI-Addr is not within any of them. It’s as simple as that.
>
>What if the GI-Addr is something completely different like 140.1.0.1?

Ah, then 140.1.0.1 must be within the shared network that defines the client subnet(s). So something like :
shared-network "blah" {
  subnet 140.1.0.0 255.255.255.252 {
  }
  subnet 192.168.1.0 255.255.255.0 {
    blah blah options
    range blah;
  }
}
That allows the server to see 140.1.0.1, associate that address with a shared network, and thus find the pools/ranges it can allocate to clients.

And in case you hadn't realised, you can't use the same GI-Addr in more than one shared network.  If you do, then the server can't use it to select a unique shared network.

Simon