sending options from wrong subnet in shared-network

Brian J. Murrell brian at interlinx.bc.ca
Thu Dec 5 13:50:49 UTC 2013


I have a shared network configuration that looks like this:

shared-network foo {
    subnet 192.168.0.0 netmask 255.255.255.0 {
         option routers             192.168.0.1;
         option domain-name         "subdomain.example.com";
         option domain-name-servers 192.168.0.4;
         option subnet-mask         255.255.255.0;
         default-lease-time         21600;
         max-lease-time             43200;
    }
    subnet 10.14.80.0 netmask 255.255.248.0 {
         option routers             10.14.80.1;
         option domain-name         "subdomain.example.com";
         option domain-name-servers 10.14.80.8, 10.14.80.9, 10.14.80.6;
         option subnet-mask         255.255.248.0;
         range dynamic-bootp        10.14.80.100 10.14.83.254;
         default-lease-time         21600;
         max-lease-time             43200;
         next-server                10.14.80.6;
    }
}

The problem is that clients seem to be getting an address from one
network and options from the other in their reply:

08:19:07.216363 52:54:00:0f:ce:31 > 52:54:00:19:d9:08, ethertype IPv4 (0x0800), length 344: (tos 0x10, ttl 128, id 0, offset 0, flags [none], proto UDP (17), length 330)
    10.14.80.6.bootps > 10.14.81.56.bootpc: BOOTP/DHCP, Reply, length 302, xid 0x19d908, Flags [none]
          Your-IP 10.14.81.56
          Server-IP 10.14.80.6
          Client-Ethernet-Address 52:54:00:19:d9:08
          file "/pxelinux.0"
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: ACK
            Server-ID Option 54, length 4: 10.14.80.6
            Lease-Time Option 51, length 4: 10
            Subnet-Mask Option 1, length 4: 255.255.255.0
            Default-Gateway Option 3, length 4: 192.168.0.1
            Domain-Name-Server Option 6, length 4: 192.168.0.4
            Hostname Option 12, length 11: "lotus-19vm8"
            Domain-Name Option 15, length 13: "subdomain.example.com"

That particular client is defined later in the configuration file as:

    host lotus-19vm8 {
        hardware ethernet 52:54:00:19:D9:08;
        filename "/pxelinux.0";
        next-server 10.14.80.6;
        option host-name="lotus-19vm8";
        ddns-updates on;
        ddns-hostname "lotus-19vm8";
        ddns-domainname "subdomain.example.com";
    }

So why is the server sending the options from the wrong subnet
declaration?  Certainly it would be more clear if both the address and
options being offered were from the wrong subnet declaration but it
seems odd that the server would be giving an address from one subnet
declaration and options from the other.

Ultimately what I am trying to achieve here is assigning
"fixed-address"es for the first subnet and dynamic addresses for the
second subnet where I have host declarations for all of my hosts and the
dynamic ones look like the above and the fixed ones look like:

    host lotus-6-mgmt {
        hardware ethernet 00:e1:76:d6:12:06;
        fixed-address 192.168.0.6;
        option routers 10.14.80.1;
        filename "/pxelinux.0";
        next-server 10.14.80.6;
        option host-name="lotus-6-mgmt";
        ddns-updates on;
        ddns-hostname "lotus-6-mgmt";
        ddns-domainname "subdomain.example.com";
    }

Cheers,
b.

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