More weird formats (which at least work in chrome/mac, and the mac implementation of getaddrinfo()):

http://184.11274826/ http://184.172.2634/

The rule here is that the last (but apparently only the last) numeric component may encode multiple bytes.

I use this one all the time:

127.0.0.1 == 127.1

10.0.0.1 == 10.1

192.168.0.1 == 192.168.1

I wasn't aware of that shortcut, that's very useful.

It's especially useful for some IPv6 addresses.

IPv6 has a different representation format, where one (and only one) sequence of fields containing only 0 bytes may be replaced by a single '::', turning '2001:0:0:1:0:2' into '2001::1:0:2'.

I never quite understood why they chose to reuse the colon as a separator character, because this is problematic when you want to append a port number. '2001::1:0:2:8080' could either be '2001:0:0:1:0:2 on port 8080', or '2001:0:1:0:2:8080 on the default port'. The following (ugly) syntax is used to resolve that ambiguity: [2001::1:0:2]:8080.

More IPv6 hackery: When using a link-local address (every interface has a link-local IPv6 address), you can append a zone index to the address in the brackets as routing information of where to send the link local request. For windows it's the interface number, for Unixes it's the interface name.

To test this out, first find a link-local address on your network. To find all link-local addresses on eth0, use this command to ping the all-nodes link-local multicast group:

  ping6 -I eth0 -c 2 ff02::1

Now append the percent sign and zone index to the address and connect to the host on a port that is probably open.

  lynx https://[fe80::21e:67ff:fe08:d500%eth0]:443/

I often use 0 == 0.0.0.0 == localhost

This is not true. 0.0.0.0 may end up at localhost for you, but it's not localhost. I just get: PING 0.0.0.0 (0.0.0.0): 56 data bytes ping: sendto: No route to host

Which system do you use that this works on?

I don't know about the OP, but in Ubuntu Precise "ping 0" pings to 127.0.0.1.

I can't explain why.

From what I can tell, the use of '0' or '0.0.0.0' as a destination address is not official. It should only be used as a source address. From RFC 5735 - Special USe IPv4 Addresses:

   0.0.0.0/8 - Addresses in this block refer to source hosts on "this"
   network.  Address 0.0.0.0/32 may be used as a source address for this
   host on this network; other addresses within 0.0.0.0/8 may be used to
   refer to specified hosts on this network.

Support for it looks to be flaky. 'ping 0' and 'ping 0.0.0.0' work for me on various Linuxes ("64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.026 ms"), but not on Windows 7 ("sendto: Cannot assign requested address") or Windows Server 2003 ("Destination specified is invalid").

IPv6 behaviour seems to be the same: "ping6 ::" pings to ::1: (localhost).

This is intriguing, really :)

EDIT: oh, you already pointed to the RFC :)

My understanding is that 0.0.0.0 is the opposite of localhost as binding a daemon to 0 would bind that service to every interface and on any available IP. This means if you have MySQL (for example) listening on 0, it's not just listening on your localhost address but also on any WAN / LAN IPs you have as well.

aha. i didnt know this. thanks

I didn't use bypass tool you've mentioned.

This small ruby script

    #!/usr/bin/ruby
    a, b, c, d = $*[0].split('.').map(&:to_i)
    i = a * 256**3 + b * 256**2 + c * 256 + d
    puts "dec: http://#{i}"
    puts "hex: http://0x#{i.to_s(16)}"
    puts "oct: http://0#{i.to_s(8)}"

..yields the following:

    % ip2dword 184.172.10.74
    dec: http://3098282570
    hex: http://0xb8ac0a4a
    oct: http://027053005112

My apologies, I've removed that line.

Looks like Internet Explorer recognizes them all as the same address (when I hover over the link, it shows the link target in dotted decimal). Chrome does the same thing for 1, 3, and 4 but doesn't like the number > INT_MAX. Firefox thinks they're all different.

I recognize the other formats, but what format is "http://7393249866/"? It opens about:blank in chrome. How is it distinguished from the format above it?

7393249866 mod 2^32 is 3098282570. I'm not convinced you can do that - although it works in Firefox, telnet and ping don't like it.

Edit: I highly doubt that this is standard behavior. I suspect that implementations that permit this are storing the number in a 32 bit integer and not checking to see that it was truncated.

ping and other command line tools don't mind it for me on OSX, I don't know what the distinction between them would be though.

    $ ping 7393249866
    PING 7393249866 (184.172.10.74): 56 data bytes
    64 bytes from 184.172.10.74: icmp_seq=0 ttl=47 time=259.042 ms

It seems to work in Safari as well. I sort of understand the dword format, but why would this be useful, or a standard?

Funny. http://7393249866/ resolves to http://255.255.255.255/ in Opera (on linux), it appears to do saturating math for the overflow.

It works fine in my Opera 12.16 for Linux (amd64).

Same here:

    $ uname -a
    Linux GFMPC-056 3.11.2-1-ARCH #1 SMP PREEMPT Fri Sep 27 07:35:36 CEST 2013 x86_64 GNU/Linux

You can also mix and match octal, decimal, and hex on the different octets.

Hexa addresses can be in one single number too:

http://0xb8ac0a4a/

What? It's bothered me for years that IP addresses aren't just bitfields. Why would you use a format other than this?

10.0.0.1 or 0x0a000001?

4.2.2.1 or 0x04020201?

Mostly readability and speed of typing, I would think.

http://7393249866/ doesn't seem to work in chrome as it doesn't believe it's a link. Entering it directly in the URL-bar doesn't work either. All of the others is shown as `184.172.10.74` on mouse-over.

Went to RSnake's website and encoded the address of Facebook to post on my wall. Facebook does not let me post it. After 3 or 4 tries, it blocked my account.

Does anyone know why Facebook does that?

Probably because this "trick" is often used by spammers to obfuscate URLs.

More encodings:

http://[0:0:0:0:0:ffff:b8ac:a4a]

http://asdf:qwerty@3098282570/

http://asdf:qwerty@[0:0:0:0:0:ffff:b8ac:a4a]:80

(Might get a security/phishing warning on the last two links in some browsers.)

And another way of doing the first one:

http://[0::0:ffff:b8ac:a4a]/

No warnings in Chrome