not getting same ip for same MAC

Christopher Barry christopher.r.barry at
Wed Aug 8 15:02:17 UTC 2018

configs and leases file here:

I'm booting an embedded device via u-boot over tftp, and I am getting
one IP during boot, and another IP once Linux comes up. This has not
always done this, and I am struggling to find a solution.

I have a pool with 2 IPs in it, and I boot 2 devices in a test fixture.
Each device position (regardless of physical device) always gets the
same IP, as I am deleting the leases file / restarting dhcpd between
invocations of the test, and I power on the devices in the same order.

Now, device1 boots the tftp image, gets (as it should), then
when Linux boots and requests an IP, it is getting (which it
should NOT do). I have the lease time and max lease time set to 1 (but
I have set these values to many other values up to a couple minutes
with no change).

To be clear, this has worked for over a year, and suddenly is not
working. The Linux platform running dhcpd is centos 7. The dhcpd
version is in the pastebin link above.

In the leases file it can be seen that the uid value is different
between u-boot and linux, even though the MAC is the same. I'm
suspicious that this is what is confusing dhcpd.

How can I MAKE it only use MAC?



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