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List:       sun-managers
Subject:    DNS subdomain reverse lookup (long)
From:       "Thomas Carter" <TCarter () memc ! com>
Date:       2000-05-31 21:37:13
[Download RAW message or body]

I'm having trouble with a DNS configuration I've inherited. First the
background:

We are a subdomain from our parent company. For example, they are B.com and
we are A.B.com.  However, we share the same IP subnet space, e.g. 111.222.
###.### (Actually part of a Class B subnet) for both domains.

/etc/named.boot looks like as follows:
directory       /etc/named
primary         0.0.127.IN-ADDR.ARPA.           named.127.0.0
primary         222.111.IN-ADDR.ARPA.           named.222.111
primary         A.B.com.                named.A
cache           .                               named.cache
; added for internet access
forwarders      111.222.101.5

The forwarders is the IP address of the parent company's DNS server, e.g.
dns.B.com.

named.cache looks like this:
.                       99999999        IN      NS      dns.B.com
;
dns.B.com          99999999        IN      A       111.222.101.5

NS entries in named.222.111:
                        IN      NS      dns.A.B.com.
dns.A.B.com.    IN      A       111.222.200.101
                        IN      NS      dns.B.com.
dns.A.B.com.    IN      A       111.222.100.101


The problem has to do with reverse lookup on servers in the B.com domain.
Both forward and reverse lookups on servers in the A.B.com domain work
fine. Forward lookups work fine for the B.com domain. But if I try to
perform a reverse lookup on the B.com domain, I get an error.

Command line:
# nslookup xyz.A.B.com
Server:  dns.A.B.com
Address:  111.222.200.101

Name:    xyz.A.B.com
Address:  111.222.200.103

# nslookup 111.222.200.103
Server:  dns.A.B.com
Address:  111.222.200.101

Name:    xyz.A.B.com
Address:  111.222.200.103

# nslookup abc.B.com
Server:  dns.A.B.com
Address:  111.222.200.101

Non-authoritative answer:
Name:    abc.B.com
Address:  111.222.100.202

# nslookup 111.222.100.202
Server:  dns.A.B.com
Address:  111.222.200.101

*** dns.A.B.com can't find 111.222.100.202: Non-existent host/domain

When I turn on level 2 debug on in.named, it logs the following (line
snipped out):
req: nlookup(202.100.222.111.in-addr.arpa) id 13550 type=12 class=1
req: found '202.100.222.111.in-addr.arpa' as '222.111.in-addr.arpa'
(cname=0)


I apologize for the long explaination, but does anyone have any idea on
what is wrong? I suspect it has to do with the shared IP subnet for the two
domains, but haven't been able to determine what is causing this. I've read
man pages, FAQs, PSDs, etc until my eyes crossed, and an still stumped.

Thanks for the assistance,
Thomas Carter
MEMC Southwest

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