We write only what we have run and verified
Our networking articles follow the flow of a book. Start with the preface to read from the beginning, or use each topic's core reading path to find the principles you need.
Articles
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This preface traces the endpoint–server round trip and introduces addressing, switching, routing, network design, security, and recovery.
Follow one web request through DNS, ARP, TCP, TLS, routing, and NAT, and see which values change on the way to the server and back.
See how an endpoint uses bitwise AND with IPv4 addresses and a subnet mask to classify destinations as on-link or off-link and choose its ARP target.
Size CIDR subnets for address needs and growth, calculate network and host ranges, and check VLSM allocation, overlaps, and route summaries.
Follow DHCP from a laptop's first IP allocation through lease renewal at T1, rebinding at T2, relays, and address reservations.
See how ARP finds a local destination or gateway MAC, and how each router chooses the next recipient and builds a new Ethernet frame.
How access ports assign VLANs and 802.1Q trunks preserve them, including native VLAN mismatches and failure boundaries.
How STP prevents Layer 2 loops through root election and port roles, with RSTP convergence and edge-port protection.
Bundled links do not multiply one flow's speed. Learn how LACP forms a bundle, hashing distributes flows, and failures reassign them.
Trace inter-VLAN traffic through SVIs and router-on-a-stick: gateway ARP, route lookup, Layer 2 header rewriting, and policy boundaries.
Follow route-source and metric selection into the RIB/FIB, then longest prefix match, next-hop resolution, and adjacency-based packet forwarding.
See how PCs share one public IP through NAT/PAT, how mappings return replies, and how translation, sessions, and firewall state differ.
How static routes enter the RIB, resolve Ethernet next hops, and use floating backups and remote tracking—and how failover affects existing sessions.
How OSPF forms neighbors, synchronizes LSDBs, floods changed LSAs within an area, and updates each router's SPF results, RIB, and FIB.
How enterprise networks divide switching, routing, NAT, firewall, and DHCP roles by failure impact, change scope, ownership, and redundancy needs.
Read Cisco campus reference designs by business need: distinguish roles, tiers, and L2/L3 boundaries, then check the conditions for your site.
Access, distribution, and core are roles, not device counts. Trace local, inter-VLAN, and inter-block traffic to see which tiers it uses.
Assess a small office's single-router design by its business, guest, and management access, actual throughput, and replacement time.
Design a single-tier office network with separate switches and APs, checking ports, PoE, VLANs, gateways, and failure impact.
Plan private address hierarchies across sites and clouds, and link allocations and observations in IPAM to reduce overlap and change risk.
Use 48 × 1 Gbps ports and two 10 Gbps uplinks to compare oversubscription, utilization, failure capacity, flow imbalance, and brief congestion.
Trace devices, power, conduits, VLANs, and shared services to see what fails together—and where separation reduces impact but adds work.
Compare distribution gateways and routed access: VLAN extent, ARP targets, hop-by-hop MACs, return paths, and policy placement.
Connect wiring closets to two distribution devices: gateway placement, uplink capacity, failure paths, and operational handover.
Compare switch and router redundancy: physical links, virtual gateways, alternate routes, session state, failure detection, and business recovery.
Decide when distribution blocks need a separate core using routes, summaries, failure paths, and maintenance needs—not the number of buildings.
Check branch, cloud and internet links: address rights, routes, access rules, overlaps, return paths, when to use BGP and what to hand over.
Trace public IP allocation from IANA to users, distinguish registration from BGP reachability, and identify address holders and service operators.
Follow BGP sessions and UPDATEs through route selection, local policy, iBGP distribution, and RPKI checks—and locate where a prefix stops.
Learn how route redistribution changes metrics and source information, how tags and prefix policy stop feedback, and how defaults and summaries affect traffic.
Follow employee access and file sharing to see where firewalls, IPS, NDR, DLP/DRM, zero trust, and VPNs apply—and how they limit a spreading compromise.
Compare upstream RTBH and FlowSpec with sinkhole analysis, including DDoS bottlenecks, legitimate-traffic impact, asymmetric paths, and safe withdrawal.
Turn requirements into baseline, failure, and return-to-service tests. Measure network and business recovery separately, and record unverified items.
Assess impact, compare working and failing endpoints, and restore services by importance and dependencies. Contain active compromises before restoring access.
Review IP and MAC addressing, switching, routing, and NAT through one web request and response, then connect network design with security and recovery.
Before an article is published
// REVIEW GATEEvery article goes through eight checks before publication. The same standards apply to our own work and outside submissions. We preserve each external manuscript unchanged and make a separate review copy. Review records are kept for every article.
Facts and measurements
We run the commands, calculations, and procedures and record the reproduced values in the review record. We do not publish unverified claims.
Originality
We do not copy other documents or pad the text with stilted, translated-sounding prose. We also remove stock phrases such as ‘Let's take a look at…’.
Depth
We require at least 1,000 characters, a structure organized with subheadings, and enough detail for readers to try things themselves.
E-E-A-T
We identify the writer and reviewer, state when the article was updated, and include at least one example we measured ourselves.
Internal links
We check that the article belongs in its topic and links to the relevant tool and the preceding and following articles.
Style
Korean copy, no emoji, consistent terminology: our design charter applies to the writing too.
Policy
We check for exaggeration, clickbait wording, and coverage of sensitive topics.
Rights
We verify sources and usage rights. External manuscripts are reviewed with their originals preserved unchanged.
How we write
// HOWTry it, then write it
We run the commands, check the calculations by hand, and put those values in the article. We do not include claims that cannot be reproduced.
Connect articles and tools
If you need a calculation while reading, a link takes you straight to the tool. If you want to understand the principle behind a tool, you can go straight to the article.
Identify who wrote it and when
Each article names its writer and reviewer and records its update date. See About us for the site operator.