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Asked: 2014-12-13 16:42:51 +0800 CST

How to associate a DHCP pool or subnet with declarations for a class

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I have the following working configuration for ISC DHCP server 4.1.1, which hands out fixed addresses to registered clients. Some of those clients are configured for PXE booting (for FAI and SCCM).

# General declarations
authoritative;
option domain-name            "department.example.edu";
option domain-name-servers    8.8.8.8, 8.8.4.4;
default-lease-time            86400;

class "fai" {
    match hardware;
    next-server fai.department.example.edu;
    filename "fai/pxelinux.0";
}

class "sccm" {
    match hardware;
    next-server sccm.department.example.edu;
    filename "sccm/pxelinux.0";
}

# Public network (one of many).
# Ethernet outlets are in public areas.  By policy we require users to
# register their MAC addresses, and clients obtain fixed addresses.
subnet 10.20.0.0 netmask 255.255.0.0 {
    option subnet-mask        255.255.0.0;
    option broadcast-address  10.20.255.255;
    option routers            10.20.0.1;
}

# Three of many hosts registered for fixed address assignments in the public network
host host1.department.example.edu {
    hardware ethernet ca:fe:ba:be:00:01; fixed-address 10.20.1.1;
}

host linux2.department.example.edu {
    hardware ethernet ca:fe:ba:be:00:02; fixed-address 10.20.1.2;
}
subclass "fai" 1:ca:fe:ba:be:00:02;

host windows3.department.example.edu {
    hardware ethernet ca:fe:ba:be:00:03; fixed-address 10.20.1.3;
}
subclass "sccm" 1:ca:fe:ba:be:00:03;

Now, I would like to add support for another subnet where we will hand out dynamic addresses from a pool to any DHCP client (because all Ethernet outlets on that VLAN are at the IT workbench in a secure location). The question is, what is a good way to make the existing SCCM declarations the default for the IT workbench?

# New IT workbench subnet.  I'd like the "sccm" settings to be the default
# for this subnet.
#
# The VLAN only has outlets in a secure location, so MAC address registration
# is not necessary.
subnet 192.168.1.0 netmask 255.255.255.0 {
    option subnet-mask        255.255.255.0;
    option broadcast-address  192.168.1.255;
    option routers            192.168.1.1;
    pool {
        range 192.168.1.2 192.168.1.254;
        # Point A: what declarations to put here, if anything?
    }
    # Point B: what declarations to put here, if anything?
}
# Point C: what declarations to put here, if anything?

Conceptually, I could write at Point B

    next-server sccm.department.example.edu;
    filename "sccm/pxelinux.0";

but that would be repeating myself. I'd like to take associate the subnet with the existing "sccm" class, if possible. What could I write that has the effect of

    subclass "sccm" "anything-in-192.168.1.0/24";

(I don't have to use a class for the SCCM declarations. If a group or some other mechanism works, that would be fine too.)

pxe-boot

0 Answers