IPLookup
Networking Glossary
Detailed explanations of IP addressing and networking terms. Click any term to jump to its definition.
All Terms (20)
ASN (Autonomous System Number)
An Autonomous System Number (ASN) is a unique identifier assigned to a network or group of IP addresses managed by a single organization, such as an internet service provider (ISP), cloud provider, or large enterprise. ASNs are a fundamental part of the internet's routing system — they allow different networks to exchange traffic with each other using the Border Gateway Protocol (BGP). When you see an ASN displayed in our IP lookup tool (e.g., AS13335 for Cloudflare), it identifies the network that owns your IP address. There are approximately 100,000 active ASNs worldwide. ASNs come in two formats: 16-bit (ranging from 1 to 64511) and 32-bit (ranging from 131072 to 4294967295). Knowing your ASN can help with network troubleshooting, understanding your ISP's infrastructure, and identifying whether an IP belongs to a residential ISP or a datacenter.
ISP (Internet Service Provider)
An Internet Service Provider (ISP) is a company that provides internet access to individuals and organizations. ISPs own the infrastructure — fiber optic cables, DSL lines, cable modems, satellite links, or cellular networks — that connects your home or business to the global internet. When you connect to the internet, your ISP assigns you a public IP address from their pool of addresses. Your ISP can see all of your unencrypted internet traffic, which is why many people use VPNs to protect their privacy. Examples of major ISPs include Comcast, AT&T, Verizon, Spectrum, British Telecom, Deutsche Telekom, and NTT. In our IP lookup tool, the ISP field shows the company that registered your IP address, which may be your residential ISP or a hosting provider if you are using a datacenter or VPN.
IPv4
IPv4 (Internet Protocol version 4) is the fourth version of the Internet Protocol and the most widely used IP addressing standard today. It uses a 32-bit address space, allowing for approximately 4.3 billion unique addresses. An IPv4 address is written as four decimal numbers separated by dots (e.g., 192.168.1.1). IPv4 was introduced in 1981 and has served as the backbone of the internet for over four decades. However, due to the explosive growth of internet-connected devices, the world has exhausted the pool of available IPv4 addresses. This shortage has led to the widespread use of NAT (Network Address Translation) to allow multiple devices to share a single public IP, as well as the gradual migration to IPv6. Most home and business internet connections today still use IPv4, often combined with Carrier-Grade NAT (CGNAT).
IPv6
IPv6 (Internet Protocol version 6) is the most recent version of the Internet Protocol, designed to replace IPv4. It uses a 128-bit address space, providing approximately 340 undecillion addresses — enough to assign a unique IP address to every device on the planet many times over. An IPv6 address is written as eight groups of four hexadecimal characters separated by colons (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334). IPv6 was introduced in 1998 to solve IPv4 address exhaustion and includes improvements such as built-in IPsec security, stateless address autoconfiguration (SLAAC), more efficient packet handling, and no need for NAT. Adoption has grown steadily, with major ISPs, cloud providers (AWS, Google Cloud, Azure), and CDNs (Cloudflare, Akamai) all supporting IPv6. Google reports that over 40% of users now access their services over IPv6.
VPN (Virtual Private Network)
A Virtual Private Network (VPN) creates an encrypted tunnel between your device and a remote server operated by the VPN provider. All your internet traffic is routed through this tunnel, and websites see the VPN server's IP address instead of your real IP address. VPNs are commonly used to protect privacy on public Wi-Fi, bypass geo-restrictions, prevent ISP tracking and throttling, and hide your real location from websites. When you connect to a VPN, your connection type in our IP lookup tool may show as "Possible VPN" because the IP address belongs to a known VPN provider like NordVPN, ExpressVPN, ProtonVPN, or Mullvad. It is important to note that VPNs protect your IP address from websites, but the VPN provider itself can see your traffic — which is why choosing a reputable "no-log" VPN provider is essential.
Public IP Address
A public IP address is a unique numerical identifier assigned to your internet connection by your ISP. It is visible to every website and service you visit — when you browse the web, stream video, or send email, your public IP address is included in your device's requests so that responses can be sent back to you. Unlike private IP addresses, which are used within home or office networks and are not routable on the public internet, a public IP address is globally unique. Your public IP address can reveal your approximate geographic location (usually at the city or regional level) and your ISP. Most residential connections use dynamic public IPs that change periodically, while business connections may have static public IPs that remain the same. You can see your current public IP address on our IP lookup page.
Private IP Address
A private IP address is an IP address used within a local network (such as your home or office) that is not routable on the public internet. These addresses are reserved for internal use and are typically assigned by your router using DHCP. The reserved private IP ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Devices like your computer, phone, smart TV, and printer each get a unique private IP on your home network. When these devices access the internet, your router performs Network Address Translation (NAT) to map their private IPs to your single public IP address. Private IPs allow hundreds of devices to share one public IP, which helped conserve the limited pool of IPv4 addresses. You can see your private IP by checking your device's network settings — it will likely start with 192.168, 10, or 172.16.
DNS (Domain Name System)
The Domain Name System (DNS) is the internet's address book. It translates human-readable domain names like "example.com" into machine-readable IP addresses like 93.184.216.34. When you type a URL into your browser, a DNS query is sent to a DNS resolver, which looks up the IP address associated with that domain and returns it to your browser so it can load the website. DNS is a hierarchical system — there are root servers, Top-Level Domain (TLD) servers (like .com, .org, .net), and authoritative name servers that store the actual DNS records. Common DNS record types include A (IPv4 address), AAAA (IPv6 address), CNAME (domain alias), MX (mail servers), and TXT (text records). Public DNS services like Cloudflare (1.1.1.1), Google (8.8.8.8), and Quad9 (9.9.9.9) offer faster and more private alternatives to ISP-provided DNS.
NAT (Network Address Translation)
Network Address Translation (NAT) is a technique used by routers to allow multiple devices on a local network to share a single public IP address. When a device on your home network sends a request to the internet, your router replaces the device's private IP and port with the router's public IP and a unique port number. When the response comes back, the router remembers which device made the request and forwards the response accordingly. NAT was widely adopted as a solution to IPv4 address exhaustion — it enables hundreds of devices to share one public IP. However, NAT also provides a basic layer of security by hiding internal devices from the public internet. The main downside is that it complicates peer-to-peer connections, which is why technologies like UPnP, STUN, and TURN exist. With IPv6, NAT is generally not needed because there are enough addresses for every device.
Subnet / CIDR
A subnet (short for subnetwork) is a logical subdivision of an IP network. Subnetting allows network administrators to divide a large network into smaller, more manageable segments for better performance, security, and address utilization. CIDR (Classless Inter-Domain Routing) is the modern notation used to specify subnets — it appends a slash and a number to an IP address (e.g., 192.168.1.0/24). The number after the slash indicates how many bits are used for the network portion of the address. For example, /24 means the first 24 bits are the network prefix, leaving 8 bits for host addresses (254 usable IPs). Common CIDR notations include /8 (16 million IPs), /16 (65,534 IPs), /24 (254 IPs), and /32 (a single IP). Understanding subnets and CIDR is essential for network configuration, firewall rules, and efficient IP address management.
MAC Address
A MAC (Media Access Control) address is a unique hardware identifier assigned to network interface controllers (NICs) by the manufacturer. It is a 48-bit or 64-bit address typically written as six groups of two hexadecimal digits separated by colons or hyphens (e.g., 00:1A:2B:3C:4D:5E). Unlike IP addresses, which can change based on network configuration, MAC addresses are permanent and tied to the physical hardware. They operate at Layer 2 of the OSI model and are used for communication within a local network segment. Your router uses MAC addresses to identify and assign IPs to devices via DHCP. MAC addresses can be spoofed or changed on most modern operating systems, which is sometimes done for privacy reasons or to bypass network restrictions. While your IP address is visible to websites, your MAC address is never exposed beyond your local network.
TCP/IP (Transmission Control Protocol / Internet Protocol)
TCP/IP is the fundamental communication protocol suite that powers the internet. It consists of two core protocols: the Internet Protocol (IP), which handles addressing and routing packets between devices, and the Transmission Control Protocol (TCP), which ensures reliable delivery by establishing connections, sequencing packets, and retransmitting lost data. Together, they enable devices from different manufacturers running different operating systems to communicate seamlessly across the globe. When you visit a website, your device establishes a TCP connection to the server, sends an HTTP request, receives the response, and then terminates the connection — all using the TCP/IP protocol stack. TCP/IP is often described as a four-layer model: Application (HTTP, FTP, SMTP), Transport (TCP, UDP), Internet (IP), and Link (Ethernet, Wi-Fi). Understanding TCP/IP is foundational to networking, troubleshooting, and cybersecurity.
HTTP / HTTPS
HTTP (Hypertext Transfer Protocol) is the protocol used by web browsers and servers to communicate and transfer web pages. When you visit a website, your browser sends an HTTP request, and the server responds with HTML, CSS, JavaScript, and other resources. HTTPS (HTTP Secure) is the encrypted version of HTTP, where communications are encrypted using TLS (Transport Layer Security). Websites using HTTPS show a padlock icon in the browser's address bar. HTTPS protects your data from eavesdropping, tampering, and man-in-the-middle attacks — it is essential for any website that handles sensitive information like passwords, payment details, or personal data. Most websites today use HTTPS by default, and search engines like Google use HTTPS as a ranking signal. The "s" in HTTPS literally stands for "secure," and you should always look for it before entering sensitive information on any website.
TLS / SSL
TLS (Transport Layer Security) and its predecessor SSL (Secure Sockets Layer) are cryptographic protocols that provide secure communication over a computer network. They are the technology behind the padlock icon in your browser — encrypting data transmitted between your device and the websites you visit. TLS ensures three things: authentication (you are talking to the real website, not an imposter), encryption (no one can read your data in transit), and integrity (your data has not been tampered with). TLS uses a combination of asymmetric encryption (for the initial handshake) and symmetric encryption (for the actual data transfer). Websites implement TLS by installing digital certificates issued by Certificate Authorities (CAs). SSL is the older, deprecated version and should not be used — modern systems use TLS 1.2 or 1.3. When you see HTTPS in your browser, TLS is active.
DHCP (Dynamic Host Configuration Protocol)
DHCP (Dynamic Host Configuration Protocol) is a network management protocol that automatically assigns IP addresses and other network configuration parameters (subnet mask, default gateway, DNS servers) to devices when they connect to a network. Instead of manually configuring each device's network settings, DHCP allows devices to request an IP address from a pool, and the DHCP server (usually your router) assigns one automatically. DHCP leases are temporary — the device can keep the IP for a configurable period (often 24 hours), after which it must renew the lease. This automatic assignment is why your phone, laptop, and smart TV all get different IPs on your home network without any manual setup. DHCP supports both IPv4 and IPv6 (in IPv6, it is called DHCPv6, though SLAAC — Stateless Address Autoconfiguration — is also commonly used).
Proxy Server
A proxy server is an intermediary between your device and the internet. When you use a proxy, your traffic is sent to the proxy server first, which then forwards it to the destination website. The website sees the proxy's IP address instead of your real IP address. Proxies are commonly used to bypass geo-restrictions, filter content, improve performance through caching, and provide a degree of anonymity. Unlike VPNs, most proxies do not encrypt your traffic, so your ISP can still see what you are doing. Proxies can be HTTP proxies (for web traffic only), SOCKS proxies (for any traffic), or transparent proxies (which do not hide your IP at all). While proxies are faster than VPNs because they lack encryption overhead, they are also less secure. Free proxy servers often log user activity and may inject ads or malware into web pages.
Firewall
A firewall is a network security system that monitors and controls incoming and outgoing traffic based on predetermined security rules. It acts as a barrier between a trusted internal network (like your home or office network) and untrusted external networks (like the internet). Firewalls can be hardware-based (dedicated appliances), software-based (running on your computer or server), or cloud-based (Web Application Firewalls). They inspect packets of data and decide whether to allow or block them based on rules such as source/destination IP addresses, port numbers, and protocols. Most modern operating systems include built-in software firewalls, and home routers include NAT-based firewalls. Firewalls are essential for preventing unauthorized access, blocking malware, and enforcing network security policies. They are a fundamental component of any defense-in-depth security strategy.
Ping / Latency
Ping is a network utility used to test whether a remote device is reachable and to measure the round-trip time (latency) of packets sent to that device. It works by sending ICMP (Internet Control Message Protocol) echo request packets and waiting for echo reply packets. Latency is the time it takes for data to travel from your device to a remote server and back, typically measured in milliseconds (ms). Lower latency means a more responsive connection — important for real-time applications like video calls, online gaming, and live streaming. Factors that affect latency include physical distance (fiber optic cables are fast but still limited by the speed of light), network congestion, routing efficiency, and the quality of your ISP's infrastructure. A ping of under 20ms is excellent, 20-50ms is good, 50-100ms is average, and anything above 150ms may cause noticeable lag in real-time applications.
Port / Network Protocol
A port is a virtual endpoint in a computer's network stack, identified by a 16-bit number ranging from 0 to 65535. Ports allow a single device to run multiple network services simultaneously — for example, a web server listens on port 80 (HTTP) or 443 (HTTPS), email servers use port 25 (SMTP), and DNS queries use port 53. When data arrives at an IP address, the port number tells the operating system which application should receive it. Ports are categorized into three ranges: well-known ports (0-1023, assigned to common services), registered ports (1024-49151, used by applications), and dynamic/private ports (49152-65535, used as ephemeral source ports). Understanding ports is essential for configuring firewalls, setting up servers, and troubleshooting network connectivity. A network protocol defines the rules for data exchange — common protocols include TCP (connection-oriented, reliable) and UDP (connectionless, faster but less reliable).
IP Geolocation
IP geolocation is the process of estimating the physical location of a device based on its public IP address. This is done by consulting large databases that map IP address ranges to geographic locations, based on ISP registration data, regional internet registry records, and network measurement data. IP geolocation can typically identify the city and region associated with an IP, but it cannot determine your exact street address — it is "neighborhood-level," not "street-level." Accuracy varies significantly: in urban areas with accurate ISP records, it may be within a few miles, but in rural areas, it might show a location hundreds of miles away. IP geolocation is used for localizing content, fraud detection, analytics, and geo-restriction enforcement. Our IP lookup tool uses ipinfo.io to provide IP geolocation data. Your GPS location is never used — all location data comes from IP registration records.