Pool independent GI Address

Simon Hobson dhcp1 at thehobsons.co.uk
Sun Dec 14 17:25:49 UTC 2014

Stephan Sanders <stephan at sanders.koeln> wrote:

> DHCP relay on remote routers supports only the usage one GI address.

Well that's implementation specific - it must use "an" address which is within a subnet on the remote network. But if it has more than one, how can it work out which to use ?

> 2 DHCP server (active / hot standby) has to propagate different addresses.
> Its not possible to use the same pool for both servers!
> Server A pools within
> Server B pools within
> Gi Address within (not within space of pool A or B)

Why is it not possible to use the same *subnet* for both servers ?

Also, basically why it isn't working is you have lied to the servers about the network. If they don't know that,, and are all on the same physical network (technically, same broadcast domain) then they won't work. So your config needs to be :

shared-network "foo" {
  <any shared-network specific options>
  subnet ...
  subnet ...
  subnet ...

Configure this on both servers, configure the pool(s) (or just range(s)) you want each server to allocate addresses out of, and it'll "just work". Remember that you do not have to have an address pool in a subnet - it can be empty.

The shared-network statement tells the server that the three subnets are all carried on the same wire - and so devices may be using addresses from any of them. When it gets a request with a GI-Addr in the subnet, it will know it can allocate addresses from any ranges defined in any of the three subnets.
For Server A, this means it'll allocate addresses from the subnet - assuming that's the only subnet with any pool(s)/range(s) defined in it.

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