Different IPv4 address representations

Localhost can be represented in a lot of different ways.

• localhost
• 127.0.0.1 (IPv4 address)
• [::] or :: (IPv6 address)
• 2130706433 (IPv4 in decimal)
• 0x7f000001 (IPv4 in hexadecimal)

The last two of these are particularly interesting — IPv4 addresses can be represented as plain numbers!

Decimal/Hexadecimal conversion for IPv4 addresses is relatively simple if you remember that we break IPv4 addresses up into 4 octets, where each octet is 8 binary digits. Thus

Converting to hexadecimal is trivial using the excellent Qalculate! tool.

2130706433 to hex = 0x7F000001

Common addresses

localhost

localhost → 127.0.0.1 → 0x7F000001 → 2130706433 (decimal)

Server metadata

169.254.169.254 is often used in to reference configuration data in cloud systems (just AWS?).

169.254.169.254 → 0xA9FEA9FE → 2852039166 (decimal)