上一片里，TCP 把大文件拆成带编号的小包裹。但每个包裹在网上走哪条路，由谁指挥？💻 小电脑抱着包裹来到路口，路由器就是站在那里的交警。Last leaf, TCP chopped a big file into numbered little parcels. But who decides which road each parcel takes? 💻 The little computer carries its parcel to the junction, where the router stands like a traffic cop.
第 1 步：路由表：每条路通向哪Step 1: The routing table: where each road goes
💻 小电脑抱着写有地址的包裹，走进快递分拣站。💻 The little computer carries an addressed parcel into the sorting hub.
路由器就是快递分拣站：看一眼地址 8.8.8.8，再查墙上的路由表，就知道送它走出口 1、2 还是 3。路由表是路由器的指路牌。A router is a parcel sorting hub: it reads the address 8.8.8.8, checks the routing table on the wall, and picks exit 1, 2 or 3. The table is the router's signpost.
出了分拣站，包裹能直达网站吗？Once it leaves the hub, does the parcel go straight to the website?
第 2 步：一站一站接力送Step 2: Relay it station by station
从你家到网站，中间隔着好几台路由器。每台只做一件事：看地址，选下一站。像接力赛一样传下去，包裹就到了。Between your home and the website stand several routers. Each does one job: read the address, pick the next stop. Passed along like a relay race, the parcel arrives.
半路上路断了，包裹会卡住吗？If a road breaks halfway, will the parcel get stuck?
家里的路由器是第一站，连着手机、电脑、电视，还连着运营商。哪段路断了，路由器们就互通消息，绕开断路继续送。Your home router is the first stop, linking your phone, computer and TV to the internet provider. When a stretch of road breaks, routers swap news and detour around it, keeping parcels moving.
🎮 你来当路由器（30 秒）🎮 Be the router (30 seconds)
包裹在你家，你就是沿途每台路由器：点下一站，送 4 个包裹去网站。路断了就绕开！The parcel is at your home, and you are every router along the way: tap the next stop and deliver 4 parcels to the website. Detour around broken roads!
一句话记住它：路由器 = 网络的交警：看地址、查路由表，一站一站送包裹。Remember it in one line: a router is the traffic cop of the network — it reads addresses, checks its table, and passes parcels station by station.
路由表告诉它：去某地址该走哪个出口The routing table says which exit leads toward each address每台路由器只选下一站，不管全程Each router picks only the next stop, never the whole route路断了会自动绕行，包裹照样送到Broken roads are detoured automatically — parcels still arrive
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
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