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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)
Every network on the internet needs a unique identifier to route traffic — that is what an Autonomous System Number (ASN) does. Think of it as a license plate for a network run by an ISP, cloud provider, or large enterprise. ASNs are a fundamental part of the internet's routing system; they let different networks exchange traffic using the Border Gateway Protocol (BGP). When our IP lookup tool shows you an ASN like AS13335 (Cloudflare), it's telling you which network owns your IP address. There are roughly 100,000 active ASNs worldwide, split between 16-bit (1 to 64511) and 32-bit (131072 to 4294967295) formats. Knowing your ASN helps with network troubleshooting, understanding your ISP's setup, and figuring out whether an IP belongs to a residential ISP or a datacenter.
ISP (Internet Service Provider)
Your ISP — short for Internet Service Provider — is the company that connects your home or business to the internet. ISPs own the physical infrastructure: fiber optic cables, DSL lines, cable modems, satellite links, or cellular networks that make your connection possible. When you go online, your ISP assigns you a public IP address from its pool, and it can see all of your unencrypted traffic (which is why so many people use VPNs these days). Major ISPs include Comcast, AT&T, Verizon, Spectrum, British Telecom, Deutsche Telekom, and NTT. In our IP lookup tool, the ISP field shows whichever company registered your IP — either your residential ISP or a hosting provider if you're on a datacenter or VPN.
IPv4
IPv4 stands for Internet Protocol version 4 — it is the fourth iteration of the IP standard and still the most widely used across the internet. It works with a 32-bit address space that gives us roughly 4.3 billion unique addresses. You have probably seen IPv4 addresses plenty of times: they are written as four decimal numbers separated by dots, like 192.168.1.1. IPv4 has been around since 1981 and has served as the internet's backbone for over four decades. The problem is that we have run out of available IPv4 addresses thanks to the explosion of internet-connected devices. That shortage led to NAT (Network Address Translation), which lets multiple devices share a single public IP, and it also pushed the gradual migration to IPv6. Most home and business connections still rely on IPv4, often paired with Carrier-Grade NAT.
IPv6
IPv6 is the newest version of the Internet Protocol, designed specifically to take over from IPv4. Instead of 32 bits, it uses a 128-bit address space, which gives us roughly 340 undecillion addresses — enough to assign a unique IP to every device on the planet many times over. You can spot an IPv6 address by its format: eight groups of four hexadecimal characters separated by colons, like 2001:0db8:85a3:0000:0000:8a2e:0370:7334. IPv6 was introduced back in 1998 to solve IPv4 exhaustion, and it brings built-in IPsec security, stateless address autoconfiguration (SLAAC), more efficient packet handling, and no need for NAT. Adoption keeps growing — major ISPs, cloud providers (AWS, Google Cloud, Azure), and CDNs (Cloudflare, Akamai) all support it now. Google reports that over 40% of users access their services over IPv6 these days.
VPN (Virtual Private Network)
A VPN (Virtual Private Network) creates an encrypted tunnel between your device and a remote server run by the VPN provider. All your internet traffic flows through that tunnel, and websites see the VPN server's IP instead of your real one. People use VPNs to stay private on public Wi-Fi, bypass geo-restrictions, stop ISPs from tracking or throttling them, and hide their real location from websites. When you connect to a VPN, our IP lookup tool might show "Possible VPN" as your connection type — that happens when your IP belongs to a known provider like NordVPN, ExpressVPN, ProtonVPN, or Mullvad. One thing to keep in mind: a VPN hides your IP from websites, but the VPN provider can still see your traffic. That is why picking a reputable "no-log" provider matters.
Public IP Address
Your public IP address is the unique identifier your ISP assigns to your internet connection. Every website and service you visit sees it — when you browse, stream, or send email, your public IP tags along with your requests so the responses come back to you. Unlike private IPs that only exist within your home or office network (and aren't routable on the public internet), a public IP is globally unique. It can reveal your approximate geographic location, usually at the city or regional level, plus your ISP. Most residential connections use dynamic public IPs that change periodically, while business connections often get static ones that stay the same. Check our IP lookup page to see yours right now.
Private IP Address
A private IP address lives only within your local network — your home or office — and is not routable on the public internet. These addresses are reserved for internal use and your router hands them out automatically using DHCP. The reserved ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Your computer, phone, smart TV, and printer each get their own private IP on your home network. When those devices access the internet, your router uses NAT to map their private IPs to your single public IP. This setup lets hundreds of devices share one public IP, which helped stretch the limited IPv4 address pool. You can find your private IP in your device's network settings — it probably starts with 192.168, 10, or 172.16.
DNS (Domain Name System)
DNS stands for Domain Name System, and it is essentially the internet's address book. When you type "example.com" into your browser, DNS translates that human-friendly domain name into a machine-readable IP address like 93.184.216.34. Here is how it works: your browser sends a DNS query to a resolver, which looks up the IP for that domain and sends it back so the page can load. DNS is hierarchical — it starts with root servers, then Top-Level Domain servers (.com, .org, .net), and finally authoritative name servers that hold the actual records. Common record types include A (IPv4), AAAA (IPv6), CNAME (aliases), MX (mail servers), and TXT (verification records). If your ISP's DNS is slow, you can switch to free alternatives like Cloudflare (1.1.1.1), Google (8.8.8.8), or Quad9 (9.9.9.9).
NAT (Network Address Translation)
NAT (Network Address Translation) is how your router lets multiple devices share one public IP address. Here is how it plays out: when your laptop sends a request to the internet, your router swaps your laptop's private IP and port with its own public IP and a unique port number. When the response comes back, the router remembers which device asked for it and forwards the data to the right place. NAT became widely adopted because we were running out of IPv4 addresses — it lets hundreds of devices share a single public IP. It also adds a basic layer of security by keeping internal devices hidden from the public internet. The main drawback is that it complicates peer-to-peer connections, which is why we have technologies like UPnP, STUN, and TURN. With IPv6, NAT is generally unnecessary since every device can have its own unique address.
Subnet / CIDR
A subnet (short for subnetwork) is how network admins split a large IP network into smaller, more manageable pieces. Subnetting improves performance, security, and address utilization. CIDR (Classless Inter-Domain Routing) is the modern way to specify subnets — you write an IP address followed by a slash and a number, like 192.168.1.0/24. That number tells you how many bits are used for the network prefix. A /24 means the first 24 bits are the network part, leaving 8 bits for host addresses (254 usable IPs). Common CIDR blocks include /8 (16 million IPs), /16 (65,534 IPs), /24 (254 IPs), and /32 (a single IP). Understanding subnets and CIDR is key to network configuration, firewall rules, and IP address management.
MAC Address
A MAC (Media Access Control) address is a permanent hardware identifier burned into every network interface card by the manufacturer. It is usually 48 or 64 bits, written as six groups of two hex digits separated by colons or hyphens, like 00:1A:2B:3C:4D:5E. Unlike IP addresses, which change depending on the network you are connected to, a MAC address is tied to the physical hardware and does not change. MACs operate at Layer 2 of the OSI model and are used for communication within your local network segment. Your router uses MAC addresses to identify devices and hand out IPs via DHCP. You can spoof or change your MAC address on most modern operating systems — people sometimes do this for privacy or to bypass network restrictions. Just keep in mind that while your IP is visible to every website you visit, your MAC address never leaves your local network.
TCP/IP (Transmission Control Protocol / Internet Protocol)
TCP/IP is the communication protocol suite that makes the internet work. It has two core protocols: IP (Internet Protocol) handles addressing and routing packets between devices, while TCP (Transmission Control Protocol) ensures reliable delivery by establishing connections, sequencing packets, and retransmitting anything that gets lost. Together, they let devices from different manufacturers running different operating systems talk to each other anywhere in the world. When you visit a website, your device opens a TCP connection to the server, sends an HTTP request, gets the response, and closes the connection — all powered by TCP/IP. This protocol stack is usually described as four layers: Application (HTTP, FTP, SMTP), Transport (TCP, UDP), Internet (IP), and Link (Ethernet, Wi-Fi). Understanding TCP/IP is foundational if you work with networking, troubleshooting, or cybersecurity.
HTTP / HTTPS
HTTP (Hypertext Transfer Protocol) is how your browser talks to web servers. When you visit a site, your browser sends an HTTP request and the server sends back HTML, CSS, JavaScript, and other resources. HTTPS is the encrypted version — it wraps HTTP inside TLS (Transport Layer Security) so nobody can eavesdrop on your connection. You can spot HTTPS by the padlock icon in your browser's address bar. HTTPS protects against eavesdropping, tampering, and man-in-the-middle attacks, which is critical for any site handling passwords, payment details, or personal data. Most websites default to HTTPS these days, and Google uses it as a ranking signal. The "s" in HTTPS stands for "secure," and you should always check for it before entering sensitive information on any site.
TLS / SSL
TLS (Transport Layer Security) — and its older, now-deprecated predecessor SSL (Secure Sockets Layer) — is the cryptographic protocol behind that padlock icon in your browser. TLS does three things: authentication (confirming you are talking to the real site, not an imposter), encryption (keeping your data private in transit), and integrity (making sure nobody tampered with your data). It uses asymmetric encryption for the initial handshake and symmetric encryption for the actual data transfer. Websites enable TLS by installing digital certificates issued by Certificate Authorities (CAs). SSL is outdated and insecure — modern systems use TLS 1.2 or 1.3. Every time you see HTTPS in your browser address bar, TLS is what makes it work.
DHCP (Dynamic Host Configuration Protocol)
DHCP (Dynamic Host Configuration Protocol) is the reason your devices can join a network without you having to configure anything manually. When you connect a phone, laptop, or smart TV to your Wi-Fi, DHCP automatically assigns it an IP address, along with the subnet mask, default gateway, and DNS servers. The DHCP server is usually your router, and it hands out addresses from a pool on a temporary basis — a lease that typically lasts 24 hours. When the lease expires, the device can renew it. This is why everything on your home network just works without you entering IP addresses by hand. DHCP works for both IPv4 and IPv6 (called DHCPv6 for IPv6, though SLAAC is also common).
Proxy Server
A proxy server sits between your device and the internet. When you use one, your traffic goes to the proxy first, which then forwards it to the destination website. The website sees the proxy's IP instead of yours. People use proxies to bypass geo-restrictions, filter content, speed things up with caching, and get a bit of anonymity. Unlike VPNs, most proxies do not encrypt your traffic, so your ISP can still see what you are doing. Proxies come in different types: HTTP proxies (web traffic only), SOCKS proxies (any traffic), and transparent proxies (which do not hide your IP at all). They are generally faster than VPNs since there is no encryption overhead, but they are also less secure. Free proxy servers are notorious for logging user activity and sometimes injecting ads or malware into pages.
Firewall
A firewall monitors and controls network traffic based on security rules. Think of it as a gatekeeper between your trusted internal network (home or office) and the untrusted internet. Firewalls can be hardware appliances, software running on your computer, or cloud-based Web Application Firewalls. They inspect data packets and decide whether to allow or block them based on source and destination IPs, port numbers, and protocols. Your computer likely has a built-in software firewall, and your home router has a NAT-based firewall. Firewalls are essential for preventing unauthorized access, blocking malware, and enforcing security policies. They are a fundamental piece of any defense-in-depth security setup.
Ping / Latency
Ping is the tool you use to check if a remote device is reachable and how long it takes to get a response. It sends ICMP echo request packets and waits for echo replies. The time it takes for a packet to travel to the destination and back is called latency, measured in milliseconds (ms). Lower latency means a snappier connection — critical for video calls, online gaming, and live streaming. What affects latency? Physical distance plays a role (even fiber optics are limited by the speed of light), along with network congestion, routing efficiency, and your ISP's infrastructure quality. As a rough guide: under 20ms is excellent, 20-50ms is good, 50-100ms is average, and anything above 150ms can feel sluggish for real-time applications.
Port / Network Protocol
A port is a virtual endpoint in your computer's network stack, identified by a number from 0 to 65535. Ports let a single device run multiple network services at the same time. For example, a web server listens on port 80 (HTTP) or 443 (HTTPS), email uses port 25 (SMTP), and DNS uses port 53. When data arrives at an IP address, the port number tells the operating system which application should get it. Ports are split into three ranges: well-known ports (0-1023 for common services), registered ports (1024-49151 for applications), and dynamic ports (49152-65535 for temporary use). Understanding ports helps with configuring firewalls, setting up servers, and troubleshooting network issues. The protocol (TCP or UDP) defines how data is exchanged — TCP is connection-oriented and reliable, while UDP is faster but does not guarantee delivery.
IP Geolocation
IP geolocation estimates where a device is located based on its public IP address. It works by consulting large databases that map IP ranges to geographic locations using ISP registration data, regional internet registry records, and network measurements. IP geolocation can usually tell you the city and region, but it cannot give you a street address — think of it as neighborhood-level, not street-level. Accuracy varies a lot: in cities with good ISP records, it may be within a few miles, but in rural areas, it could be off by hundreds of miles. Websites use IP geolocation for localizing content, fraud detection, analytics, and enforcing geo-restrictions. Our IP lookup tool uses ipinfo.io for this data. Your GPS location is never involved — everything comes from IP registration records.