Case Studies案例研究 / Featured Case推荐案例
900 to 100 Mbps for No Reason — Tracing It to Faulty In-Wall Cabling
网速莫名从900掉到100M：排查揪出墙内网线故障
1000M plan · FTTP1000M套餐 · FTTPIntermittent speed drop网速忽快忽慢Remote video diagnosis远程视频排查Root cause: in-wall port根因:墙内网口
A 1000 Mbps plan on a WiFi 7 router, freshly set up. In the morning, speed tests hit 900+ Mbps. By the afternoon — nothing touched, nothing moved — the same phone in the same spot tested under 100 Mbps. The ISP swore their side was fine. This is the kind of "it's haunted" fault that wastes days if you're guessing.
1000M套餐，配的是WiFi 7路由器，刚装好。上午测速稳稳900多兆，到了下午——设备没动、线没动、什么都没改——同一部手机在同一个位置，测速却掉到不足100兆。运营商一口咬定他们那边正常。这种"闹鬼"式的故障，靠猜能耗掉你好几天。
Ruling things out, one layer at a time
一层一层地排除
A random-looking speed drop can come from a dozen places, so we ruled them out in order over a video call. The WiFi 7 router — brought over from overseas — was working fine and its admin settings were correct. The ISP had confirmed the line itself was healthy. If it's not the router and not the line, the problem lives in between: the physical wiring. Luckily the customer had a laptop that could plug straight into the wall port with a cable, which let us test the wired path directly instead of guessing over WiFi.
看似随机的掉速可能来自十几个环节，所以我们通过视频通话按顺序逐个排除。那台从国外带过来的WiFi 7路由器本身工作正常、后台设置也没问题；运营商也确认线路健康。既然不是路由器、也不是线路，问题就出在两者之间——物理布线。好在客户有一台能用网线直插墙内网口的笔记本，让我们能直接测有线链路，而不是隔着WiFi瞎猜。
The culprit: an in-wall port that couldn't hold Gigabit
元凶：一个撑不住千兆的墙内网口
- The in-wall ethernet run feeding the router was damaged or poor quality, so the port kept negotiating an unstable link rate — sometimes a full 1000 Mbps, sometimes dropping to 100 Mbps.
- That single flapping port perfectly explained the "900 in the morning, under 100 by afternoon" pattern — every time it renegotiated down to Fast Ethernet, the whole connection was capped.
- The room only had two wall ports to begin with: one was completely dead, and the one in use couldn't hold gigabit. Classic botched-installer cabling.
With the root cause pinned down, we handed over a clear fix plan matched to the customer's budget — which port to re-run or replace, and how to get a stable gigabit path to the router.
- 接路由器的那段墙内网线本身或损坏、或质量不佳，导致网口一直在协商一个不稳定的链路速率——有时是满千兆1000M，有时掉到100M。
- 就是这一个"抽风"的网口，完美解释了"上午900、下午不到100"的现象——每次它降协商到百兆，整条连接就被卡住了。
- 这个房间原本就只有两个墙内网口：一个完全不通，正在用的这个又撑不住千兆。妥妥被装修/布线的人坑了。
根因锁定后，我们按客户预算给了一套明确的解决方案——哪个网口需要重新走线或更换，怎样给路由器一条稳定的千兆链路。
How to spot this one yourself
这类问题自己怎么初步判断
If your speed randomly swings between full-plan and about 100 Mbps, and both the ISP and the router check out, suspect the physical layer. On a wired connection, look at the port's link speed (e.g. in Windows adapter status): a healthy gigabit run reports 1.0 Gbps, while a bad cable or port often falls back to 100 Mbps. A connection that keeps flip-flopping between the two is the tell-tale sign of a marginal cable or wall port — not your internet plan.
如果你的网速在"满速"和"100M上下"之间随机横跳，而运营商和路由器都正常，就该怀疑物理层。用网线直连时，看一下网口的协商速率（比如Windows网络适配器状态里）：健康的千兆链路会显示1.0 Gbps，而坏线或坏口常常掉到100M。如果它在两者之间反复横跳，基本就是网线或墙内网口临界故障的典型信号——问题不在你的宽带套餐。
Result最终结果
A "haunted" speed drop pinned to a single faulty in-wall port — diagnosed remotely, with a budget-matched fix plan so the 1000M plan could finally run at 1000M.
一个"闹鬼"式的掉速，最终锁定在一个坏掉的墙内网口——远程排查定位，并给出按预算落地的方案，让1000M套餐真正跑到1000M。