IPv4 Address
An IPv4 address is a unique identifier made up of a 32-bit number written as four octets (e.g., 192.168.1.10). Each octet ranges from 0–255.
Dynamic Host Configuration Protocol (DHCP)
A DHCP server is a network server that automatically assigns IP addresses and other network configuration parameters to devices (clients) on a network. Its main job is to eliminate the need for a network administrator to manually assign IP addresses to every single device.
Private IP (RFC 1918)
Used inside local networks (LANs) and are not routable on the public internet — must go through NAT (Network Address Translation).
Automatic Private IP Addressing (APIPA)
When a Windows device can't reach a DHCP server, it auto-assigns itself an IP address in the 169.254.0.0/16 range.
If you see an IP address starting with 169.254, your device has given itself an APIPA address. (Range: 169.254.0.1 – 169.254.255.254.)
APIPA is activated when the device's attempt to get a "real" IP address fails completely. This is usually due to:
- DHCP Server is Down or Unreachable: The server that gives out IP addresses is offline.
- Network Cable Issue: A faulty Ethernet cable can prevent communication with the DHCP server.
- Switch/Router Problem: The network equipment between the device and the DHCP server has failed.
- Driver or NIC Issue: A problem with the device's own network card or its software.
Loopback / Localhost
Loopback is used to test network functionality on your own device — data is sent out and received back internally. Range: 127.0.0.0 – 127.255.255.255