Hiya, I only recently learned that when addressing an Internet server/host by IPv4 address, it is possible to not use the standard dotted decimal notation (abc.def.uvw.xyz) but instead use any of a number of alternative formats; for example it is possible to specify the IP address in all-decimal dword format, or as an octal or hexadecimal number, etc.
If this is news to you, and if you have a bit of time to waste, you could read a bit more here: http://www.reddit.com/comments/6usfd/case_study_is_php_embarrasingly_slower_than_java/c04xgjf http://www.pc-help.org/obscure.htm Now, I was really surprised to learn of all of this, as this info is hardly ever mentioned everywhere, and it seems to me that even many fairly seasoned IT people aren't aware of these possibilities. E.g. the http://www.3com.com/other/pdfs/infra/corpinfo/en_US/501302.pdf that's linked from the OpenBSD FAQ also doesn't mention these alternative notations at all. So I wonder: Does anyone know whether these alternative notations (dword/octal/hexadecimal...) are officially *supposed* to work? Or is it more of an accident that they do? Are there any RFCs on this? (A cursory search didn't turn up anything that seemed appropriate.) Presumably it's a matter of the TCP/IP stack that they do work? But it seems not all tools appear to do support this; e.g. I couldn't find a way to look up 2172650943 with whois or host, but ping and ftp work fine, as does the traditional notation 129.128.5.191. Firefox however appears to work fine with dword/all-decimal IPv4 addresses, as does lynx. So I wonder what's expected behaviour here, and whether the tools that don't work with alternate notations should work? Also, does all of this have implications for pf.conf? A bit of googling told me that black hats sometimes try to use these alternate notations to get around restrictions. Thanks and regards, --ropers
