Short Leases for PXE-Clients

Tom Schmitt TomSchmitt at
Fri May 18 14:43:12 UTC 2007


I'm using isc-dhcpd v.3.0.3 and have several PXE-clients. Because of the PXE-boot these clients take two leases (one for the PXE-networkcard without an UID and one for the OS with an UID).

Because the first lease is only needed while booting, I want to give out only a short leasetime. So I put the following statement into my dhcpd.conf:

class "PXE" {
    match if substring(option vendor-class-identifier, 0, 9) = "PXEClient";
        log (info, " Matched my PXE-rule ");
        ddns-updates false;
        default-lease-time 600;
        max-lease-time 900;

After reloading the dhcp-config, I saw the " Matched my PXE-rule " messages in my Logfile, so I assumed all works as expected.

But when I looked with a packetsniffer I saw still the global-leasetime of 12 hours in the DHCPACK-packets. The server seemes to ignore the lease-time-statement in the class-statement!

Could anybody give me a hint where to look for the source of this problem?

(the global-lease-time and the one in the PXE-class are the only lease-time-statements in my config. There are no lease-time-statements in the subnet-configuration or in a host- or group-configuration)

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