Addressing
IP address
A logical address that identifies an interface on an IP network.
Aliases
IPv4IPv6Example
192.168.1.20 can identify a laptop on a LAN.
Phase 1 · Reference
Plain-language definitions for core networking terms, with tiny examples.
A logical address that identifies an interface on an IP network.
IPv4IPv6192.168.1.20 can identify a laptop on a LAN.
A smaller IP network carved out of a larger address block.
CIDR192.168.10.0/24 contains 256 addresses.
The router a host uses when the destination is outside the local subnet.
GatewayA home PC may use 192.168.1.1 as its gateway.
A link-layer hardware identifier used on local networks.
Switches learn which MAC address lives on each port.
A protocol that maps an IPv4 address to a MAC address on the local link.
Who has 192.168.1.1? Tell 192.168.1.20.
The naming system that resolves human-readable names into records such as IP addresses.
Domain Name Systempacket.school can resolve to an A record.
A protocol that automatically gives hosts IP settings such as address, mask, and gateway.
A phone joins Wi-Fi and receives an IP lease.
A connection-oriented transport protocol with reliability and ordered delivery.
HTTPS usually runs over TCP port 443.
A lightweight transport protocol without built-in delivery guarantees.
DNS queries often use UDP port 53.
A control protocol used for diagnostics and network error messages.
ping uses ICMP echo request and reply.
A layer-2 device that forwards frames based on MAC addresses.
A switch connects devices inside the same LAN.
A layer-3 device that forwards packets between IP networks.
A router moves traffic from your LAN to the internet.
A policy enforcement point that allows or blocks traffic.
Block inbound TCP 22 except from admin IPs.
Translation that lets private addresses share or map to public addresses.
Network Address TranslationMany home devices share one public IP.
A logical layer-2 network separated on shared switching infrastructure.
Guest Wi-Fi can live in a separate VLAN.
The largest packet size a link can carry without fragmentation.
Maximum Transmission UnitEthernet commonly uses an MTU of 1500 bytes.
A limit that prevents packets or cached records from living forever.
Time To LiveRouters decrement IP TTL at every hop.
The time it takes for data to travel from one point to another.
A 20 ms ping is lower latency than a 120 ms ping.
The percentage of packets that fail to reach their destination.
Video calls degrade when packet loss rises.
Slash notation that describes an IP network prefix length.
/24 means the first 24 bits are the network part.
A protocol that encrypts and authenticates application traffic.
HTTPS is HTTP protected by TLS.
The routing protocol autonomous systems use to exchange internet routes.
ISPs use BGP to announce reachable prefixes.
A distributed system that serves content from locations closer to users.
Content Delivery NetworkA CDN can serve images from a nearby edge node.
An encrypted tunnel that carries traffic across another network.
A remote employee connects to office resources over VPN.