[CLUE-Tech] DNS - reverse lookups for a classless subnet

[Dave Anselmi]

Eric Batalden wrote:

> i have used the DNS-HOWTO to setup up my DNS server.
> it seems to work just fine, resolves names and address
> both ways.  it is my understaning is that for my
> server to "play nice" with the other servers i need to
> account for my classless subnet.  i am looking after
> only eight IP's.

For any names you provide A records for (the names that go with your 8
IPs) you should provide PTR records to do the reverse mapping.  Because
there are two different zones involved, they may be delegated
differently (i.e., your NS is authoritative for the A records but your
ISP is authoritative for the PTR records).

I don't know how ISPs usually handle this but you should ask.  At least
you can use dig or nslookup to ask your ISP's nameservers about your IP
addresses.  See if they tell you something generic or what you've set
up.

If you have different forward and reverse mappings, you may have
problems using some systems (e.g., mail) that try to screen bogus
traffic based on DNS.

The best resource I think you'll find is the DNS & BIND book by Cricket
Liu.  4th edition covering BIND 9 is out.  If you don't want to buy it,
try various libraries--I got it through Arapahoe County once.

Dave