DHCPd IP dispatch

Question

For my tests, the following was done with 2 virtual machines. The server is under CentOS7 and the client under Windows 10 (MAC : 08:00:27:bd:3d:ab).

After every modification on the server side, I perform a release/renew on the client to check if it get the IP I want.

Here is the configuration :

authoritative;
ddns-update-style none;
default-lease-time 28800;
max-lease-time 36000;
allow bootp;

next-server 192.168.0.254;
filename "pxelinux.0";

shared-network {
    subnet 192.168.0.0 netmask 255.255.255.128 {
        option broadcast-address 192.168.0.127;
        option routers 192.168.0.1;
        option ntp-servers 192.168.0.1;
        option domain-name-servers 192.168.0.1;

        class "matchHW" {
            match hardware;
        }

        group {
            deny unknown-clients;
            subclass "matchHW" 1:08:00:27:bd:3d:ab;
        }

        group {
            deny unknown-clients;
            host win10 {
                hardware ethernet f8:00:27:bd:3d:ab;
                fixed-address 192.168.0.13;
            }
        }

        pool {
            allow members of "matchHW";
            option routers 192.168.0.3;
            option domain-name-servers 192.168.0.3;
            range 192.168.0.40 192.168.0.49;
        }

        pool {
            allow unknown-clients;
            option routers 192.168.0.2;
            option domain-name-servers 192.168.0.2;
            range 192.168.0.30 192.168.0.39;
        }
    }
}

In this specific configuration, I don't understand why the Windows client get for it's IP 192.168.0.30 with .1 for it's GW. I expect it get 192.168.0.40 with .3 for it's GW.

If I switch the 2 MACs (08:00:27:bd:3d:ab, f8:00:27:bd:3d:ab) to get a static IP, it works (get 192.168.0.13). If I edit these MAC to come with my client with an unknown MAC, it works too (get 192.168.0.30).

The final goal of my configuration is to serve IP for 3 "groups" :

static IP for known MAC
dynamic IP for known MAC
dynamic IP for unknown MAC

Each of these groups will have specific routers and DNS configuration.

Does anyone has an idea ?

score 0 · Answer 1 · answered Feb 26 '20 at 10:45

I found a solution, thanks to these two links :

Here is my working configuration :

shared-network {

    subnet 192.168.0.0 netmask 255.255.255.128 {
        option broadcast-address 192.168.0.127;
        option routers 192.168.0.1;
        option ntp-servers 192.168.0.1;
        option domain-name-servers 192.168.0.1;

        # known clients - dynamic IP
        pool {
            allow known-clients;
            range 192.168.0.40 192.168.0.49;
        }

        # unknown clients - dynamic IP
        pool {
            allow unknown-clients;
            deny known-clients;
            option routers 192.168.0.2;
            option domain-name-servers 192.168.0.2;
            range 192.168.0.30 192.168.0.39;
        }
    }

}

# known clients - dynamic IP
group {
    deny unknown-clients;
    option routers 192.168.0.3;
    option ntp-servers 192.168.0.3;
    option domain-name-servers 192.168.0.3;

    host dyn-A {
        hardware ethernet f8:00:27:bd:3d:ab;
    }
}

# known clients - static IP
group {
    deny unknown-clients;
    option routers 192.168.0.1;
    option ntp-servers 192.168.0.1;
    option domain-name-servers 192.168.0.1;

    host win10 {
        hardware ethernet e8:00:27:bd:3d:ab;
        fixed-address 192.168.0.13;
    }
}

DHCPd IP dispatch

1 Answers1