nanog mailing list archives

Re: comcast ipv6 PTR


From: Chris Adams <cma () cmadams net>
Date: Wed, 9 Oct 2013 20:18:17 -0500

Once upon a time, Barry Shein <bzs () world std com> said:
It's very useful for blocking spammers and other miscreants -- no
reason at all to accept SMTP connections from troublesome
*.rev.domain.net at all, no matter what the preceding NNN-NNN-NNN-NNN
is.

If you are going to block like that, just block anybody without valid
reverse DNS.  If you don't trust provider foo.net to police their users,
why trust them to put valid and consistent xx-xx-xx-xx.dyn.foo.net
reverse?

I only see a use for reverse DNS for router interfaces (for useful
traceroute info) and servers (and only really SMTP servers).  Most of
the rest is fluff, often out-of-date, uselessly auto-generated, etc.

-- 
Chris Adams <cma () cmadams net>


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