Networking Fundamentals · lesson 4 of 17 · 15 min
IPv4 address structure
An IPv4 address is a 32-bit number written as four decimal octets separated by dots:
192.168.1.100
. Each octet is 8 bits, so each ranges from 0 to 255.
- Network vs. host portion
- An IP address has two parts: the
network portion (identifies the network) and the host portion (identifies the device on that network). The subnet mask determines where the split is. Address classes (historical) Class A: 1.0.0.0 – 126.255.255.255 — /8 default mask — large organizations. Class B: 128.0.0.0 – 191.255.255.255 — /16 default mask — medium organizations. Class C: 192.0.0.0 – 223.255.255.255 — /24 default mask — small networks. Private address ranges (RFC 1918) These ranges are not routed on the internet and are used for internal networks: 10.0.0.0/8 · 172.16.0.0/12 · 192.168.0.0/16 IPv4 has ~4.3 billion addresses — exhausted in 2011. NAT (Network Address Translation) extends IPv4 by letting many private addresses share one public IP. IPv6 (128-bit addresses) is the long-term solution.
IP address ranges
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