Odd lease and renewal times

Gregory Sloop gregs at sloop.net
Sat Oct 7 00:21:59 UTC 2017

I have a number of stations and printers that are renewing their leases at intervals shorter than n/2 - where N is the lease time.
[In this case, 14400s]

However if I look in dhcp.leases - the lease is written as 10m. 

I'm running a fail-over pair.

mclt is 30m

default-lease-time 14400;
max-lease-time 14400;

I can't seem to grok where the 10m lease time is coming from.
Any ideas where to look?

[Oh, and yes, as far as I can tell, only some clients are so afflicted.]

Here's a excert of leases

lease {
  starts 6 2017/10/07 00:03:39;
  ends 6 2017/10/07 00:13:39;
  tstp 6 2017/10/07 00:18:39;
  tsfp 6 2017/10/07 00:13:37;
  cltt 6 2017/10/07 00:03:39;
  binding state active;
  next binding state expired;
  hardware ethernet 00:00:00:00:00:00;
  set ddns-fwd-name = "some-stupidhost.somedom.com";
  set ddns-txt = "00 ... db";
  set ddns-rev-name = "";
  client-hostname "abc-hp-4200";
[Yeah, this is an HP printer/print-server, but some Windows clients do it too.]

Another random case is a Windows laptop.

It DOES get a 4h lease, but then makes DHCPREQUEST's at crazy intervals.
Sometimes it's 90m, others 90s. [I can't find any consistency...]
This is a wireless device, I believe, would it make a new request if it were dropped and re-connected to the network?

Nothing's "broken." Everything is getting leases as they should, but I'm trying to understand why.
Mostly looking for a good methodology and reasoning to start running the oddities down.

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