IP addressing & ports

IPv4 addresses

• 32 bits, written as four octets of 0–255, e.g. 192.168.1.10.
• A subnet mask (e.g. 255.255.255.0, i.e. /24) splits the address into a network part and a host part.
• A /24 network holds 256 addresses; the first is the network address and the last is the broadcast, leaving 254 usable hosts.

IPv4 vs IPv6

IPv6 uses 128 bits (eight groups of four hex digits) to escape the exhaustion of the 32-bit IPv4 space.

Well-known ports