Reverse DNS RFCs and Recommendations

Thu Oct 31 02:01:58 UTC 2013

On October 30, 2013 at 19:07 Valdis.Kletnieks at vt.edu (Valdis.Kletnieks at vt.edu) wrote:
 > On Wed, 30 Oct 2013 21:33:38 -0000, Nolan Rollo said:
 > 
 > > So in the four examples below, 3 of them preface the IP with an alpha
 > > character. Charter however, starts the rDNS off with a number. I'm not arguing
 > > with anyone but what potential problems could that cause with DNS?
 > 
 > Only if the system involved got on the net before 3com did (as RFC1123
 > specifically relaxed this requirement back in 1989).
 > 
 > And at that point, Indiana Jones would say "It belongs in a *museum*".
 > 

Back when I put Boston University on the net, pre-DNS, an accidentally
included host name with a leading digit submitted for the HOSTS.TXT
file brought down probably over half the net, many many unix systems.

There was a bug in the program which converted from the HOSTS.TXT
format to the unix /etc/hosts format. It went into a loop filling the
root partitions which in those days hung a unix system hard, and many
sites used unix systems as their main or only internet connection, no
fancy on-site routers back then.

Typically sites loaded the new HOSTS.TXT file after (or exactly at)
midnight automatically so not a lot of systems staff around to recover
which made it all the more painful.

So I heard a lot about this "no leading digits in host names rule" the
next day though when everyone calmed down it was agreed that the
conversion program shouldn't have behaved so poorly.

-- 
        -Barry Shein

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