Classless zones - & Dynamic Updates

Barry Margolin barmar at
Wed Mar 29 22:30:38 UTC 2000

In article <F2413A849CC9D211AC3500805FFE3E97099352 at swan.bcsc.GOV.BC.CA>,
Evans, Lorne R ISTA:EX <Lorne.Evans at> wrote:
>	I took a quick peek at both the archives and  RFC 2317 - but came up
>empty.  Are there any restrictions on Dynamic Updates of Classless
> zones?  The W2K MSFT Server Resource Kit doc states:
>		"NOTE Dynamic update does not work with classless
> zones.  If you need to dynamically update PTR resource records,
>do not use classless zones".
>		I am curious as to whether this is a generic DNS Server
>restriction - BIND and W2K DNS Server - or - just a  W2K DNS client / DHCP
>Server  restriction.  As well - could somebody possilby provide insight as
>to why this might be a restriction?

The general problem is that the client doesn't know the name of the reverse
domain to update.  Classless reverse domains are essentially a trick that
someone discovered.  With normal reverse DNS, if you have the address
w.x.y.z, you can assume that you need to update an entry in the zone, but with classless the reverse zone
can be just about anything.

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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