shared subnet declaration behavior between 2 pools

[Patrick Trapp]

All things being equal, I don’t know how it handles this. In our network, each pool in the shared network is assigned based on class matching (or not matching). In our case, each class matches a different type of device which gets a different configuration in addition to receiving an address from a different pool.

I’m not sure, looking at your configuration here, why you need a shared network. What are you trying to accomplish?

In our case, we have multiple networks that are all reaching the DHCP server via a particular network. In order for ISC DHCP to accept a request from network Z when the request came through network X, we define shared networks so that the server accepts the request as valid. Otherwise, it rejects the request. You don’t seem to have that type of scenario in your example.

What problem are you trying to fix with a shared network?

From: dhcp-users [mailto:dhcp-users-bounces at lists.isc.org] On Behalf Of project722
Sent: Monday, October 9, 2017 3:10 PM
To: Users of ISC DHCP <dhcp-users at lists.isc.org>
Subject: shared subnet declaration behavior between 2 pools

Hello. im curious as to how dhcpd determines what pool to pull a lease from in a shared subnet declaration. for ex on our server we have:

shared-network "Market 1" {
        option domain-name "example.com<http://example.com>";
                subnet 192.168.1.0 netmask 255.255.255.0 {
                option broadcast-address 192.168.1.255;
                option routers 192.168.1.1;
                pool {


                       failover peer "dhcp-failover";
                       range 192.168.1.10 192.168.1.254;

        }
        subnet 192.168.2.0 netmask 255.255.255.0 {
                option broadcast-address 192.168.2.255;
                option routers 192.168.2.1;
                pool {

                        failover peer "dhcp-failover";
                        range 192.168.2.10 192.168.2.254;


               }
}

I would suspect that the broadcasts that come through these routers/gateways determine the pool that dhcp assigns a lease from. So, if a client requests is seen by the sever comes from 192.168.1.1 it will get a lease out of that pool, and if it sees that the client requests cvomes from 192.168.2.1 it will get a lease from that pool. Is my understanding correct on this? If that is correct, then what happens when the 192.168.1.0 network gets full? Does dhcpd have some type of algo that allows it to assign a lease from the 192.168.2.0 pool in order to prevent an out of leases condition?

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