What Is an IP Address? IPv4, IPv6 and Local Addresses

An IP address is not a permanent personal identity. It identifies a source or destination in IP communication, and one device can have several addresses on different interfaces. An address may also be assigned to another device later. When diagnosing a connection, first identify the interface and address actually in use.

Recognizing IPv4 and IPv6

IPv4 addresses contain 32 bits and are commonly written as four decimal numbers separated by dots. IPv6 addresses contain 128 bits and use hexadecimal groups separated by colons. These are documentation examples, not live servers to connect to:

IPv4: 192.0.2.25
IPv6: 2001:db8::25

The double colon in IPv6 compresses consecutive zero groups and can appear only once in an address. A larger address space does not automatically encrypt a connection. HTTPS, authentication, and appropriate firewall rules remain necessary with either protocol.

Your local address may differ from your Internet exit

A computer can show 192.168.1.20 while an external service sees another IPv4 address. The router may use NAT, and the provider may also use CGNAT. A VPN or proxy can change the exit used by the traffic that passes through it.

The private IPv4 ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Not every address beginning with 172 is private: that block covers 172.16 through 172.31. Separate private networks can reuse these addresses.

Read the prefix and gateway too

In 192.168.1.20/24, 24 is the network prefix length. It helps determine which destinations are directly connected. Other destinations follow the routing table, often through a default gateway. A DNS server has a different job: helping resolve names.

On Windows, inspect interface configuration with:

ipconfig /all

On Linux, inspect addresses and the default routes for both address families:

ip -br address
ip route show default
ip -6 route show default

On macOS, ifconfig lists interfaces; do not assume Linux's ip utility is installed. VPN, Ethernet, and Wi-Fi interfaces may all appear. Find the one carrying the traffic rather than copying the first address in the output.

Collect useful evidence without exposing everything

A support request should identify the operating system, active interface, address family, and whether the failure concerns the local network or an Internet destination. Before posting a complete configuration publicly, remove unrelated device names, MAC addresses, and organizational information. If IPv4 succeeds while IPv6 fails, investigate them as separate paths instead of reducing the observation to “the Internet works.”

Next: dynamic versus static addresses. References: private IPv4 allocation and IPv6 specification.