Pool independent GI Address

[Simon Hobson]

Stephan Sanders <stephan at sanders.koeln> wrote:

> Each LAN-segment (>1000 sites) terminates on a router with its own dhcp-relay.
> on this interface are configured two IP addresses from different subnets. Its not a cisco, but on a cisco it will be configured as described from you:
>>  ip address 10.10.1.1 255.255.255.248
>>  ip address 10.11.1.1 255.255.255.248 secondary
> 
> On this router the dhcp-relay is configured for two different dhcp-servers.
> Limitation in this release is the definition of only one GI Address for both targets.
> So the GI IP for the relayed packets is in this case 10.10.1.1 for both servers.

OK, absolutely nothing unusual so far.

> The router / dhcp relay has a routed connection to both dhcp-server.
> Both servers will receive the discover from 10.10.1.1. Server A has a pool 10.10.1.0/29.
> Server B has only 10.11.1.1/29.

No, what you mean is that Server A has a **SUBNET** 10.10.1.0/29. 10.10.1.0/29 is **NOT** an address pool. For that *SUBNET*, and a GI-Addr of 10.10.1.1, your *RANGE* could be 10.10.1.2 to 10.10.1.6. In the terminology of the ISC server configuration, a *POOL* is a scope containing one or more *RANGES*.

> Both servers can't use the same pools due different routing issues.

Still struggling to think of a valid reason for that, but never mind.

> Thats the reason why my intention was to use the option 82 for the poolselection independent
> from the GI-address.

Option 82 will not help you at all - it'll be the same value sent to both servers. Just configure as I said earlier with a shared network and it will work automagically.

Server A :
shared-network "site1" {
  subnet 10.10.1.0 255.255.255.248 {
    router 10.10.1.1 ;
    range 10.10.1.2 10.10.1.6 ;
  }
  subnet 10.11.1.0 255.255.255.248 {
  }
}

Server B :
shared-network "site1" {
  subnet 10.10.1.0 255.255.255.248 {
  }
  subnet 10.11.1.0 255.255.255.248 {
    router 10.11.1.1 ;
    range 10.11.1.2 10.11.1.6 ;
  }
}


Given the small subnets, and large number of sites, sounds like a POS setup.