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While working on math, I encountered a number and wondered if it had any significance. So, in the browser search bar I entered it ("0.693"). I got redirected to the IP address 0.0.2.181, which resulted in an "unreachable" error message.
Why did I get redirected to this IP address?
MCMastery
Posted 2017-09-17T21:09:27.523
Reputation: 403
47
The browser address bar sees a . and thinks it is an IP address.
This gets passed to Windows to do a DNS lookup:
> nslookup 0.693
Server: UnKnown
Address: 192.168.42.129
Name: 0.693
Address: 0.0.2.181
Note:
693 = 256 * 2 + 181
So 0.693 gets translated to 0.0.2.181.
Prefix the value with '.
DavidPostill
Posted 2017-09-17T21:09:27.523
Reputation: 118 938
8Also, many browsers have an actual search bar next to the address bar. Typing the search in there works as well. And there are also browsers who can search by typing g search phrase in the addressbar, such as Opera, Vivaldi and other chromebased browsers. – LPChip – 2017-09-17T21:37:00.040
1@LPChip Yes. My FF is configured with a combined search/url bar (field). I had to enter http://0.693 to reproduce. – DavidPostill – 2017-09-17T21:38:34.520
1I might be mistaken, but it seems to be because it has a dot so it is identified as url which goes to dns lookup, and for some reason Windows is happy to resolve it as ip address. – PTwr – 2017-09-17T21:40:20.413
@LPChip you can also assign keywords in FF like that. I always use a separate search box so I'll just need Ctrl+L for entering addresses and Ctrl+K for searching – phuclv – 2017-09-18T05:54:58.883
8Prefixing with ? usually starts a search and prevents all further processing. In your case, when you prefix with ' you get a search term that contains the apostrophe. – Joey – 2017-09-18T06:57:16.990
@Joey In my case I get the same result with a ? prefix as with a ' prefix. – DavidPostill – 2017-09-19T06:09:06.207
@David, because the search engine tends to ignore the '. But the ? won't even be part of the search term, as opposed to the '. – Joey – 2017-09-19T08:38:59.087
@Joey Hmm. I get https://www.google.com/search?q=%3F0.693&ie=utf-8&oe=utf-8&client=firefox-b-ab in the search bar. The ? is encoded as %3F. I do have FF configured to have a combined URL and Search bar though. – DavidPostill – 2017-09-19T19:22:19.883
7
DavidPostill explained why you got redirected but didn't touch on how the number changed from 0.693 to 0.0.2.181.
What's going on here is that while IP addresses are normally described as <number>.<number>.<number>.<number> they are really just 32 bit unsigned values, the dot notation is for convenience and really is just the value split into 4 8-bit groups separated with dots. While input normally is in the 4 group notion the parsers always accept it as a number.
693 = 256 * 2 + 181.
Loren Pechtel
Posted 2017-09-17T21:09:27.523
Reputation: 2 234
5
See also, Why does pinging 192.168.072 (only 2 dots) return a response from 192.168.0.58? for a more complete explanation.
– Bob – 2017-09-18T03:09:56.9934You missed the part of my answer that explains it ... – DavidPostill – 2017-09-18T09:40:50.427
You need to escape <number>.<number>.<number>.<number> with backticks, because Stack Exchange's markdown parser is dumb and strips anything that resembles HTML rather than escaping it. – IMSoP – 2017-09-18T12:53:08.827
7
The reason 0.693 becomes 0.0.2.181 has been explained by DavidPostill. In short, the string looks like a valid IP address
Now to search for any terms use Ctrl+K (works in Firefox and Chrome) or Ctrl+E (only in Firefox). That'll trigger a search instead of letting the browser to guess if that's a valid address or not
phuclv
Posted 2017-09-17T21:09:27.523
Reputation: 14 930
6ln(2) at first sight. – YSC – 2017-09-18T14:39:48.820
Are you sure you entered it in a search bar and not an address bar? – David Schwartz – 2017-09-18T16:57:15.347