IP addresses and 10 decimal digits are sometimes used in place of domain names, usually in a web URL. This is a bad, error-prone idea for anything but the most transitory information, since the whole point of using a domain name is that it won’t change if the IP address does, so these types of numeric URL’s should not be used for long term. The two types of domain name aliases are described below:
- IP addresses. You sometimes see a web URL with the IP address specified instead of the domain name, as in the following:
http://209.118.52.173/home/list/index.html
You can convert a domain name to an IP address by pinging it, as in “ping www.yahoo.com”, and reading the response provided. In this case, you can convert an alias IP address to a domain name by doing an NSLOOKUP, although the mapping is not one-to-one — more than one domain may point at the same IP address.
- 10 digits. You sometimes see just a 10 digit number for a domain name, as in the following:
http://3124567890/home/list/index.html
The number 3124567890 is just the decimal representation of an IP address, usually represented by 32 binary bits divided into 4 sections and written for human consumption like 186.61.31.82.
The fastest way to find out the regular IP address of a domain specified with a decimal number is to ping that decimal number, which will then display the IP address in the ping response, whether or not it reaches the site. Mathematically, you can also convert a decimal IP to a regular IP with the following steps:
- Hexadecimal. Convert the number into Hexadecimal by hand, with a calculator, or with the dec2hex function in Excel.
- Truncate. Take the right-most eight hex digits.
- Decimal. Convert the digits in sets of two into the four decimal IP numbers, by converting each set of two hex digits into decimal by hand, with a calculator, or with the hex2dec function in Excel.