Restarting DHCP safely whilst avoiding partner-down state

[sthaug at nethelp.no]

> The release notes indicate that a "gentle shutdown" feature was added
> in the past and then subsequently removed because the semantics chosen
> caused operational issues - but what these were isn't known because
> the associated bug report isn't publicly available.

See the discussion thread at 

https://lists.isc.org/pipermail/dhcp-users/2014-June/017958.html
https://lists.isc.org/pipermail/dhcp-users/2014-July/017970.html

Steinar Haug, Nethelp consulting, sthaug at nethelp.no