Re: [SLUG] Sites on IP

From: Paul M Foster (
Date: Mon Apr 10 2006 - 11:52:19 EDT

Richard Morgan wrote:

> Quoting Paul M Foster <>:
>> Two questions:
>> 1. Since many sites can share the same IP, is there any way to tell
>> all the websites which share an IP?
>> 2. Assuming you have a "reseller account" with a hosting company,
>> where they give you two IPs for your sites, is it possible or probable
>> that they have also given someone else those same IPs? Is this common
>> practice or not?

> Yes, it's very common to "oversell" IP's since they are such a precious
> thing,
> nowadays. You should be able to find all of the hosts on a given IP with
> reverse DNS and some commercial web hosting services, like Also,
> Netcraft may give you that information, too.

Reverse DNS won't do it. I tried.

Here's my understanding of how this works. Correct me if I'm wrong.
Let's say server alfa is the authoritative DNS server for 50 domains.
Its BIND tables show all the translations from sitename to IP. But a DNS
query supplies a sitename and asks for an IP. Alfa is glad to oblige,
but that query doesn't say anything about what *other* sites share that
IP. Now, I don't know much about how DNS works. I don't know how those
DNS tables are populated. Are there CNAME entries, A entries, PTR
entries for each site in the tables? But how would you get a flush of
those tables? Trying reverse DNS didn't do it. I'll supply the IP
offlist, if you like (I don't want that IP up on the internet forever
for people to hack). translates to Their reverse DNS requires


Paul M. Foster
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