ARP is how devices on a local network answer the question: 'I know the IP address—but what's the MAC address?' This simple broadcast-and-reply protocol makes Ethernet work, but its trusting design creates security vulnerabilities every network administrator should understand.
Your device faces a decision with every packet: can I reach this myself, or do I need help? The default gateway is where packets go when the destination is beyond your reach.
MAC addresses solve the last mile of networking—IP gets packets to your network, but MAC addresses get them to the right physical port on the right machine.
A hub broadcasts everything to everyone—creating a network where all devices share bandwidth, collisions, and each other's secrets. Here's why switches made them obsolete.
Your devices need to talk to each other before they talk to the world. A LAN creates that private neighborhood—fast, trusted, and under your control.
A MAN connects an organization's buildings across a city—too spread out for a single LAN, too local to rent long-haul connections. It's the network you build when you outgrow one building but own your geography.
Network bridges create quiet neighborhoods within noisy networks, learning which devices live where and only forwarding traffic that actually needs to cross the boundary.
Every packet that crosses the Internet faces a choice at each hop: which way next? Routers are the decision-makers—examining destinations, consulting maps, and forwarding traffic toward where it needs to go.
Every device on your network wants to talk, but not to everyone. Switches solved the chaos of shared networks by giving each conversation its own private channel.
WANs connect networks across cities, countries, and continents—but distance imposes costs that physics won't let us escape. Understanding those costs explains every WAN technology choice.
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