IPv4 addresses are 32-bits long, written in decimal format, and separated by periods.
IPv6 addresses are 128-bits long, written in hexadecimal format, and separated by colons. IPv4 addresses cannot be used as is in IPv6, but IPv6 does support a special class of addresses: the IPv4-mapped address.
In an IPv4-mapped address, the first 80 bits are set to zero, the next 16 bits are set to 1, and the last 32 bits represent the IPv4 address.
IPv4 address IPv4-mapped address (for use in IPv6) 192.0.2.1 ::ffff:192.0.2.1