[nsd-users] enumerate an ipv6 reverse zone in 2 minutes

Anand Buddhdev anandb at ripe.net
Wed Dec 10 21:59:19 UTC 2014

On 10/12/14 22:32, A. Schulze wrote:

Hi Andreas,

> till yesterday I thought it is impossible to find hosts in an ipv6
> subnet by asking the dns server.
> At least if I use random interface identifier.
> That assumption is wrong:
> http://7bits.nl/blog/posts/finding-v6-hosts-by-efficiently-mapping-ip6-arpa

This is an old and well-known technique.

> problem:
> dig @ns.nlnetlabs.nl. ns -> NOERROR
> dig @ns.nlnetlabs.nl. ns -> NXDOMAIN
> 2 queries to tell: there is no host in the subnet 2a04:b900:1000:0::/64
>                    there are no subnets in 2a04:b900:1000::/56

This is exactly how the name server is supposed to answer. In fact, not
only NSD, but all other protocol-compliant name servers, such as BIND,
Knot and PowerDNS, will all respond the same way. Look up the term
"empty non-terminal". This manner of response is not specific to NSD.

> My question: would it be possible to modify nsd to answer queries in a
> different way?

I don't think so. It would break the DNS protocol. But just out of
curiosity, what kind of response did you have in mind.



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