Field Guide · concept

Also known as: Internet Protocol address, IPv4, IPv6

An IP address is a numeric label assigned to each device on a network that uses the Internet Protocol, identifying the host so that packets can be routed to it.1

192 168 1 10 11000000 10101000 00000001 00001010 network (mask 255.255.255.0) host four 8-bit octets = 32 bits · the subnet mask says where network ends and host begins
An IPv4 address is 32 bits written as four dotted octets. The subnet mask splits it into a network portion — shared by every host on the same LAN — and a host portion that uniquely names the device within that network.

Overview

IP addresses come in two versions: IPv4, a 32-bit value written as four dotted numbers (like 192.168.1.10), and IPv6, a 128-bit form created because the pool of IPv4 addresses ran short. An address is bound to a device’s NIC and is paired with a subnet mask that says which leading bits identify the network and which the individual host.

Addresses are usually handed out automatically by DHCP when a device joins a network, though servers and infrastructure often get static addresses that never change. On home and office networks, a block of private addresses is reused behind a router that performs network address translation (NAT), sharing one public address among many internal devices.

Routing works entirely on these numbers: every router between source and destination looks only at the destination address to decide the next hop, which is what lets a packet cross the world without any single device knowing the whole path.

IPv4 vs IPv6

The jump to IPv6 was driven by exhaustion of the older, smaller address space:

Trait IPv4 IPv6
Size 32 bits 128 bits
Notation Dotted decimal 192.168.1.10 Hex groups 2001:db8::1
Address count ~4.3 billion ~3.4 × 10³⁸
Typical assignment DHCP + NAT DHCP / autoconfiguration
Why it exists Original design Relieve IPv4 exhaustion

Where it fits

The IP address is how a router and gateway decide where a packet should go, both within a LAN and across a WAN. To reach a GopherTrunk capture node — to stream its decoded calls or open the daemon’s web console — you connect to its IP address on the local network, so giving each node a stable, known address (static, or a DHCP reservation) makes a multi-node site far easier to manage and script against.

Sources

  1. IP address — Wikipedia, on the numeric label that identifies a host, subnet masks, and IPv4 versus IPv6. ↩

See also