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On 01/17/00 at 15:09, Suzanne Swift wrote:
Re: www vs no.www
From: Global Homes Webmaster
Date: Monday, January 17, 2000
Time: 8:54:00 pm
> Thanks for the help. Two more questions:
>
> 1. Can QuickDNS be administered remotely?
Not without something like Timbuktu. As someone Jesse Proudman pointed out,
you can use AppleTalk file sharing to open domain files, but that's not really
a fully functional remote admin set-up.
> 2. What does a reverse record do? Is it necessary? If so, how do I
> configure it?
A PTR (reverse) record maps a numeric IP address to a domain name --
essentially the opposite of an A record. For most things they are not
absolutely necessary. In some situations, though, servers may not want to talk
to other hosts that don't have reverse DNS. For example, some IRC (internet
relay chat) servers don't allow connections from hosts whose reverse DNS
doesn't match the domain that the client claims to be from (people who abuse
IRC sometimes use IP 'spoofing' to try to hide their identities). Also, some
mail servers like for other hosts to at least _have_ PTR records, whether they
match the remote host's claimed domain name or not -- again, a relatively
crude check for IP spoofing.
In order for you to configure reverse DNS for your IP addresses, you must
first have the reverse domain(s) delegated to your name server. It's probably
currently delegated to your ISP. Reverse domains are NOT the same as your
regular 'forward' domains. To do a reverse look-up of an address, w.x.y.z, you
would perform a query for a PTR record for the domain 'z.y.x.w.in-addr.arpa.'
Note that the order of the numbers in the in-addr.arpa domain is the reverse
of the actual address. In order for you to do your own reverse DNS (in the
simplest case), you would need to have the domain 'y.x.w.in-addr.arpa'
delegated to you by your ISP (or whoever currently has authority for it). You
would then create a domain file for it on your QDNS server and, for each of
your IP addresses (w.x.y.z), create a PTR record:
z.y.x.w.in-addr.arpa. PTR hostname.domain.com.
If you do not have a full class C block of addresses (w.x.y.0 - w.x.y.255), it
gets more complicated. In that case, you would need to work with your ISP to
have them do whats called 'classless delegation' of your reverse domain(s),
which is not for the faint of heart. A lot of ISPs are reluctant to do it
because either they don't want to complicate their own DNS, or they don't
understand how to do it to begin with. It's often easier, especially if you
only have a few addresses, to simply tell the ISP what you want the PTR
records for your addresses to be and ask them to add the records to their name
servers. Any decent ISP should be willing to go at least that far.
Christopher Bort
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