Use this glossary while reading our guides. Each term below is linkable via #term anchors.
A numeric identifier for a device on a network. Public IPs are visible on the internet; private IPs are used inside local networks.
The most common IP format using four numbers like 8.8.8.8. IPv4 space is limited, which is why IPv6 exists.
A newer IP format using hexadecimal groups like 2001:4860:4860::8888. It provides a much larger address space.
The system that maps domain names (example.com) to IP addresses so browsers can connect to websites.
A DNS record used for reverse lookups: it maps an IP address back to a hostname. PTR records are commonly used by email servers and for diagnostics.
A lookup that asks "what hostname is configured for this IP?". It typically uses a PTR record under in-addr.arpa (IPv4) or ip6.arpa (IPv6).
A protocol/service used to retrieve registration information for domains and allocation/ownership info for IP address ranges. It's not the same as IP geolocation.
A number that identifies a network/operator on the internet (an autonomous system). ASNs help route traffic across networks (BGP).
A company that provides your internet connection (home/mobile). Your public IP address is typically assigned by your ISP.
A notation for IP ranges like 203.0.113.0/24. It indicates how many bits are fixed in a network prefix, defining the size of a subnet.
A technique that lets many private devices share one public IP address via a router. It's why devices inside your home network aren't directly reachable from the internet.
A large-scale NAT system used by ISPs that shares public IPv4 addresses across many customers using the 100.64.0.0/10 range (RFC 6598). It can block inbound connections and port forwarding.
A Virtual Private Network encrypts your traffic and routes it through a VPN server, helping reduce tracking and protect data on untrusted networks.
A server that forwards your traffic. Proxies can change apparent IPs but often don't encrypt traffic like a VPN.
An IP address that is routable on the public internet. It's what websites see when you connect from home or mobile networks.
An internal network address (RFC1918) that is not routable on the public internet, such as 10.x.x.x or 192.168.x.x.
A public IP address that can change over time, typically assigned by your ISP via DHCP.
A public IP address that stays the same over time. Often required for hosting services or consistent remote access.
Dynamic Host Configuration Protocol automatically assigns IP addresses to devices on a network.
Address Resolution Protocol maps an IP address to a device's MAC address on a local network.
The shortage of available IPv4 addresses, which led to widespread use of NAT, CGNAT, and IPv6 adoption.
A router feature that directs inbound traffic on a public IP/port to a specific device on a private network.
The routing protocol used between networks on the internet to exchange routes and reachability information.
A DNS record that maps a hostname to an IPv4 address.
A DNS record that maps a hostname to an IPv6 address.
A DNS record that maps one hostname to another hostname (an alias).
A DNS record that specifies the mail server responsible for receiving email for a domain.
A DNS record that delegates a domain to specific authoritative name servers.
A DNS cache duration (in seconds) that tells resolvers how long to keep a record before refreshing it.
DNS Security Extensions add cryptographic signatures to DNS records to prevent tampering and spoofing.
A routing method where multiple servers share the same IP and the network routes users to the nearest one.
