How networks actually work
Routing, NAT, DNS and the rest — the mechanics rather than the analogies, so the next problem is one you can reason about instead of search for.
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ARP and MAC Addresses: Finding the Hardware
How a host finds the MAC behind an IP, why ARP never leaves the local network, and how a stale cache entry produces a confusing partial outage.
beginner -
Computer Networking Basics: How Data Moves Between Machines
Understand how data travels between computers: encapsulation, addressing, routing, and protocols. A clear, mechanism-first guide to networking fundamentals.
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DNS over HTTPS: What It Hides and What It Does Not
DoH encrypts the query, not the destination. Why it breaks split-horizon DNS and content filtering, and how it differs from DNS over TLS.
intermediate -
DNS Scavenging: Why Stale Records Vanish
Understand DNS scavenging: how aging and scavenging remove stale records, why records disappear, and how to configure it safely.
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DNS Zones Explained: Zone vs Domain, Delegation, SOA
Understand DNS zones: what a zone is, how it differs from a domain, delegation, SOA records, zone transfers, and forward/reverse zones.
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How DHCP Works: DORA, Leases, and Failure Modes
Understand DHCP: the DORA exchange, lease lifecycle, renewal timing, and failure modes like exhausted scopes and conflicting servers.
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How DNS Lookup Works: Full Resolution Path
Understand the DNS lookup process from stub resolver to authoritative server, including caching at each hop and why changes take time to propagate.
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How Routing Works: Packet Paths and Decisions
Understand how routers forward packets: longest-prefix match, default routes, and why packets can get lost. A clear, step-by-step explanation of IP routing.
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How to Read a Routing Table: route print and ip route Explained
Learn to read a routing table: columns, metric, and how to spot the entry sending traffic the wrong way. Covers route print and ip route.
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MTU and Fragmentation: Why Large Pages Hang
Small pages load, large ones hang, and a VPN is in the path. How Path MTU Discovery works and why a firewall dropping ICMP silently breaks it.
intermediate -
Subnet Mask Explained: How IP Addressing Really Works
Understand how subnet masks split IP addresses into network and host parts. Learn to calculate reachability without a router, and why /24 is just a convention.
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Symmetric NAT: Why It Breaks Hole Punching
Understand symmetric NAT, how it defeats hole punching, how to detect it, and what you can do—including when your carrier controls it.
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TCP vs UDP: What Each Guarantees and Costs
Understand the real differences between TCP and UDP: reliability, ordering, overhead, and when to choose each. Includes a comparison table and common misconceptions.
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Types of NAT Explained: Full Cone, Restricted, Symmetric
Understand full cone, restricted cone, port restricted, and symmetric NAT. How each handles packets, and why NAT type matters for peer-to-peer connections.
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VLANs Explained: Tagging, Trunks, and the Native VLAN
One switch behaving as several. Access ports against trunks, how 802.1Q tagging works, and the native VLAN mistake that quietly bridges two networks.
intermediate -
What Is NAT? Network Address Translation Explained
Learn what NAT does, why it breaks inbound connections, and what it does and doesn't do for security. Understand the NAT table and common misconceptions.