IP address
Also known as: internet protocol address
An IP address is a numerical identifier assigned to each device on a network so traffic can be routed to it. IPv4 addresses are 32-bit numbers written as four octets (like 192.168.1.10); IPv6 addresses are 128 bits.
An IP (Internet Protocol) address is the numerical identifier assigned to a device's network interface so other devices can send traffic to it. Like a postal address for data, it serves two roles at once: identifying the host and locating it within a network, which is what allows routers to forward packets across the internet.
An IPv4 address is a 32-bit number written in dotted-decimal notation as four octets, each 0-255 — for example, 192.168.1.10. Every address splits into a network portion and a host portion, with the dividing line defined by a subnet mask or CIDR prefix (192.168.1.10/24 means the first 24 bits identify the network). Certain ranges are reserved as private addresses (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) for use inside local networks; devices using them reach the internet through Network Address Translation (NAT), which maps private addresses to a public one.
Because the IPv4 space allows only about 4.3 billion addresses, the industry is transitioning to IPv6, which uses 128-bit addresses written in hexadecimal (such as 2001:db8::1) and provides an effectively inexhaustible supply. Addresses can be assigned manually (static) or automatically via DHCP, and DNS translates human-readable names like achievable.me into IP addresses.
The CCNA exam tests IP addressing in depth: identifying network and host portions, subnetting with CIDR prefixes, recognizing private ranges, configuring NAT, and comparing IPv4 with IPv6 address types. Fluency with binary-to-decimal conversion and subnet math is essential for exam day.
Key takeaways
- An IP address uniquely identifies and locates a device's network interface for packet routing.
- IPv4 uses 32-bit dotted-decimal addresses split into network and host portions by a subnet mask or CIDR prefix.
- Private address ranges (10.x, 172.16-31.x, 192.168.x) require NAT to reach the public internet.
- IPv6 uses 128-bit hexadecimal addresses to overcome IPv4 exhaustion.
- Addresses are assigned statically or dynamically via DHCP, and DNS maps names to addresses.