[Herefordshire] I am in a real bind!!!

[Andrew Hodgson]

-----Original Message-----
From: herefordshire-bounces at mailman.lug.org.uk
[mailto:herefordshire-bounces at mailman.lug.org.uk] On Behalf Of John Hedges
Sent: 21 June 2005 13:28
a real bind!!!

>On Tue, Jun 21, 2005 at 11:00:59AM +0100, Andrew Hodgson wrote:
>> -----Original Message-----
>> From: herefordshire-bounces at mailman.lug.org.uk
>> [mailto:herefordshire-bounces at mailman.lug.org.uk] On Behalf Of John
Hedges
>> Sent: 21 June 2005 09:58
>> 
>> >On Tue, Jun 21, 2005 at 08:58:10AM +0100, Andrew Hodgson wrote:
>> >> Hi,
>> >> 
>> >> I am wondering whether any of you on the list can help me with a bit
of a
>> >> DNS quandary I am in.
>> >> 
>> >> I am going on broadband tomorrow and my ISP has given me an IP block
>> >> 81.2.105.208/28.  I have to host PTR records on my DNS server using
the
>> > subnetted style 208-223.105.2.81.in-addr.arpa. - this is fine.  
>> 
>> [...]
>> 
>> >Does this help you any - especially the last part?
>> 
>> >    http://www.sm5sxl.net/~mats/text/internet/dnsbind/ch09_05.htm
>> 
>> It just confirms really what I already knew about the messy delegation
>> involved.  As I said the ISP has taken care of this on the public side,
so
>> either I copy this on the private DNS server (and risk not being able to
>> resolve PTR records for other IP addresses in the larger subnet)

>This doesn't sound so bad :) All you lose is reverse DNS for around
>200 ADSL connected hosts. You could put them in /etc/hosts - does that
>get used for reverse lookups?

It isn't that bad, its just the principal and something I wanted avoiding if
possible.  /etc/hosts won't get used for clients doing the dNS lookups, I
think.  Another thing I could do is somehow populate the local copy of my
zone with ISP information, but it seems a bit poitless and petty to me, and
the script would have to work on getting the RDNS, especially if they are
delegated in similar ways to the way my blocks are allocated :(.

>> , create a
>> single zone for each IP in the subnet

>How many files is it? 14? It doesn't sound too painful.

No and is the way I will go if my last method doesn't work.  One other thing
I looked at over lunchtime is that using the method 3, if I am disconnected
from the net and the cache is blank, the RDNS wouldn't work because of not
being able to contact the root nameservers or the primary/secondary
nameservers at the ISP who hold the cname records.

>> or use the same zone as the public DNS
>> server, populate it with different records and let the private server
find
>> it from the root records - when it comes to looking up the cname, the
>> private server will already have the relevant zone, so _should_ use it as
>> opposed to looking up the zone from the DNS referrer.  I am betting that
the
>> last version will work, unless I am proved wrong either by someone
telling
>> me or when it falls over tomorrow!

>It's worth a try :) You could write a script to read the whole reverse
>dns from your isp and build a local /24 zone file periodically by
>merging in your own ips/hostnames.

See above - I hadn't actually read this far before replying.  Here is a
website with some more ideas, although this guy is very pro DJBDNS suite and
also is slightly hard to understand, but has some good ideas:

http://homepages.tesco.net/~J.deBoynePollard/FGA/avoid-rfc-2317-delegation.h
tml 

The first example he gives is a bit beyond me, especially as it uses some of
the more complex Bind syntax, but the second one is what I am proposing in
option 2 (separate zone files), I think.

Thanks.
Andrew.


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