dhcpd (isc-dhcp-server) not using part of address range

Question

dhcpd (isc-dhcpd-4.3.4 under Debian) ignores part of specified address range.

I have the subnet 10.24.32.0/22 assigned to interface:

10.24.32.0/22 dev net0  proto kernel  scope link  src 10.24.32.1

So the possible address range is 10.24.32.1 to 10.24.35.254, right?

I specified the dynamic address range of 10.24.33.1 to 10.24.35.250 in configuration file:

subnet 10.24.32.0 netmask 255.255.252.0 {
        range 10.24.33.1 10.24.35.250;
        option routers 10.24.32.1;
        authoritative;
}

and it silently ignores the 10.24.34.x range. Devices get addresses of 10.24.33.x and 10.24.35.x but not .34. The server prefers to reuse address from the .33. and .35. ranges instead of using addresses from the unused .34. range.

I also tried splitting the range:

subnet 10.24.32.0 netmask 255.255.252.0 {
        range 10.24.34.1 10.24.34.254;
        range 10.24.33.1 10.24.33.254;
        range 10.24.35.1 10.24.35.250;
        option routers 10.24.32.1;
        authoritative;
}

and the .34. is ignored either.

The log, configured to "debug" level, doesn't show any problems.

score 0 · Answer 1 · answered Jul 24 '16 at 11:34

Do you have more than ~512 active DHCP clients? Until you fill up the 10.24.33.0/24 and 10.24.35.0/24 ranges and the server logs there's no more addresses available there's no bug. The DHCP server is free to allocate or reuse addresses as it sees fit.

dhcpd (isc-dhcp-server) not using part of address range

1 Answers1