automatic reverse and forwarding zones

[Bjørn Mork]

Marco Moock <mo01 at posteo.de> writes:

> Hello,
>
> how do ISPs automatically create the reverse and forwaring zones for
> their customers IP pools?
>
> For example one of their clients has the IP 2001:db::3.

We mostly don't do this for IPv6.  It's a pointless exercise, IMHO.

We give every customer/site a /48.  Statically defining 2^80 forward and
reverse entries per customer is obviously impossible.  It can in theory
be scripted, and I believe some ISPs do that. But there is no way you
can encode 80 bits more compact and readable than most of those
addresses, so you end up with names that are long and unreadable
compared to the address they point to.  That's not why we do DNS.

There is one exception in our network: We do DNS for a few small pools
only used for IA_NA addresses. The addreses are used on CPE WAN
interfaces and will show up in traceroutes.  Some customers asked for a
name, like they're used to with IPv4. So I added that since these pools
are small enough to allow static entries.  The pool is locked to a
specific BNG and the size is fixed.  We can therefore make unique and
readable names using only a small part of the 128 bit address.  We copy
those bits directly as hex digits into the name.  No need to complicate
things by translating the variable part.

A couple of examples:

2001:4610:a:60::430
2001:4610:a:60::2
2001:4610:a:60::f00

We don't use $GENERATE for this since the data is generated by scripts
anyway.  And I don't think $GENERATE handles hex digits very well anyway?

> Is it possible to let bind create that automatically for certain zones?

Possible, but only for very small pools.  Note that $GENERATE only is a
short form for easier hand editing of zone files on the primary
server. The zone is expanded on load and zone transfers etc will contain
the expanded data set. It doesn't save any resources.  Only editing.


Bjørn