classless delegation, and 3 other q's

Barry Margolin barmar at
Sun Nov 21 07:25:59 UTC 1999

In article <011b01bf3397$1b675ba0$a179aac1 at>,
John <Johnny at> wrote:
>does anyone know about classless delegation?
>it seems to be a way, or a "workaround" to the fact that you used to be
>able to do reverse dns only if you had a whole C-class.
>our uplink, the university of vienna, uses this so we can do reverse dns
>ourselves, even though we have only a 64 ip-block assigned.
>however, on irc, some sites dont seem to recognize this and reverse map
>our addresses like what kind of
>problem is this?

Some old resolvers don't expect to encounter CNAME records when performing
PTR queries, so they get confused by classless delegation.

>and one last question, the primary NS is configured to forward querys to
>another NS (which isnt even the one authoritative for the
>zone above us)- does that make sense? it also has the line "slave" in
>named.boot, which, so it says, "leads to more complete
>forwarding and should be done."

What's your question?  "slave" is the old syntax for "options
forward-only".  Without this option, if the forwarder doesn't respond, the
server will then try querying the root servers.  The "slave" option is
usually used when you're behind a firewall, so trying to query the root
servers is bound to fail, so would just be a waste of time.

Barry Margolin, barmar at
GTE Internetworking, Powered by BBN, Burlington, MA
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.

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