Curious behaviour with expired/abandoned leases not being given out

[Christopher Causer]

On Tue, Mar 10, 2020 at 10:06:35AM -0400, perl-list wrote:
> I've seen situations where one client can continuously DHCPDECLINE
> every address that is allocated essentially marking entire pools
> abandoned.  It goes like this:

Interesting thought. There are indeed many DHCPDECLINEs in the
logs. However, this isn't limited to one client; there are 349
distinct MACs in total in the last hour. The only connection is
they're almost exclusively Apple devices (MBP, iPhone etc). These
stations usually DHCPREQUEST their second offer.

A colleague suggested that something like Bonjour Sleep Proxy may be
the underlying cause. I was doubtful given that would affect all
devices doing an arp rather than Apple devices. However, after turning
on client isolation on one of the subnets we are no longer seeing
DHCPDECLINEs and the touched percentage is indeed going down for that
subnet.

So in summary thank you for the helpful replies. Although I'm still
not certain as to the underlying cause of the issue, we now have an
easy to implement workaround.

Christopher