The bind9 package includes /etc/network/if-down.d/bind9 which does "rndc reconfig". But this should only be done *after* the interface has been deconfigured not before.
NetworkManager's /etc/NetworkManager/dispatcher.d/01ifupdown run-partses only /etc/network/if-up.d and /etc/network/if-post-down.d, so when an interface is deconfigured using NetworkManager the bind9 hook script doesn't get run at all; named does not notice that the interface has been deconfigured until its next poll (which happens every 60 minutes by default).
It looks to me as if /etc/network/if-down.d/bind9 should be moved to /etc/network/if-post-down.d/.
The bind9 package includes /etc/network/ if-down. d/bind9 which does "rndc reconfig". But this should only be done *after* the interface has been deconfigured not before.
NetworkManager's /etc/NetworkMan ager/dispatcher .d/01ifupdown run-partses only /etc/network/ if-up.d and /etc/network/ if-post- down.d, so when an interface is deconfigured using NetworkManager the bind9 hook script doesn't get run at all; named does not notice that the interface has been deconfigured until its next poll (which happens every 60 minutes by default).
It looks to me as if /etc/network/ if-down. d/bind9 should be moved to /etc/network/ if-post- down.d/ .
bind 9 1:9.8.1. dfsg.P1- 4.2ubuntu3