On the control of the Internet.

Mea culpa.

That was suppose to say "How about the case where the master zone file
has beEN amputated and the secondaries can no longer get updates?

My apologies.

I'm really not sure what you're asking, and I don't know what "master
zone file has been amputated" means, but if the master server goes
unreachable, then, for each secondary, either:
  (a) it's not reachable from anywhere, in which case it doesn't really
matter what information it has because nothing will be querying it, or
  (b) it is reachable from somewhere, in which case you log in to it
from that somewhere, edit the configuration file, change "slave" to
"master", and restart BIND. (Adjust as needed for whatever DNS server
is in use, if it's not BIND.)

     -- Brett

I have been faulted for injecting "politics" into the discussion of BGP
configurations for people that ought not......

There I go again.

Have you actually read the article I posted at the top of this thread?