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Typiclal DNS lookup behaviour of browsers on diffent platforms, for IP addresses?

Answer 1

+2 A:

There is no DNS lookup done if the entire host part is numeric in nature. It could be in dotted quad format, or a single unsigned 32 bit integer. I haven't tested IPv6 yet.

bluesmoon 2010-10-30 15:28:41

Single unsigned 32 bit integer? What does such an address look like?

Amigable Clark Kant 2010-10-30 15:30:28

eg, if your IP is 10.0.0.1, then just write the bits of each number side by side, and you get the 32 bit number, so you basically have:00001010.00000000.00000000.00000001which is 00001010000000000000000000000001which, in decimal is 335544320 (if I've done my math right)

bluesmoon 2010-10-30 15:39:23

No, it's 167772161 :) 74.125.39.105 becomes 1249716073 (so in some browsers you can visit http://1249716073/ and it'll take you to Google).

SimonJ 2010-10-30 15:48:30

Thanks, @SimonJ.

Amigable Clark Kant 2010-10-31 09:27:55

Answer 2

+1 A:

There's no point in performing a lookup as there are no authoritative DNS records for these numeric "names".

Some recursive nameservers (e.g. dnscache) will respond to these kind of queries with the corresponding IP address, as if there was a real record of the form:

74.125.39.105. IN A 74.125.39.105

but this is, I assume, intended to deal with simplistic clients that assume everything is a DNS name. The most common nameserver, BIND, doesn't have this behaviour though - so don't rely on it.

SimonJ 2010-10-30 15:43:14

Thanks! I had an idea some resolvers would answer, but also wanted to know how common it is to actually ask the DNS query for IP addresses.

Amigable Clark Kant 2010-10-31 12:36:40

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Typiclal DNS lookup behaviour of browsers on diffent platforms, for IP addresses?

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