Case Studies案例研究 / Latest Case最新案例 No DSL Sync on Any Wall Port: Two Visits to Prove the Router Was Fine and the Building's Line Was Not (Exetel DSL, Zetland)
所有墙内DSL口都不同步：跑了两趟，才证明路由器没坏、坏的是楼里的线路（Exetel DSL，Zetland）
On-site · Zetland上门 · ZetlandExetelExetelDSL over the in-wall phone lineDSL 墙内电话线接入Telstra router (second-hand)二手Telstra路由器No DSL sync on any wall port所有墙内DSL口都不同步Free NBN technician booked已约NBN人员免费上门
From the wall port, a dead router and a dead line look exactly the same: you plug in, and the DSL light never comes on. There is no way to tell the two apart by staring harder. The only way to separate them is to put a router you already trust on the same socket — and on the first visit we did not have one with us. That is why this job took two trips.
从墙上那个口看过去，「路由器坏了」和「线路坏了」的样子是一模一样的：插上去，DSL 灯就是不亮。盯着看再久也分不出来。要把这两件事分开，唯一的办法是在同一个口上接一台你本来就信得过的路由器——而第一次上门时，我们身上恰好没带。这一单要跑两趟，原因就在这里。
Why we could not call it on the first night
第一晚为什么不能下结论
The customer had two second-hand routers in the flat and neither was a clean test.
The TP-Link was out immediately: it has no DSL modem in it, so on a phone-line service it cannot connect at all no matter how it is configured. That is worth saying plainly, because plenty of routers sold second-hand look the part and simply are not built for a DSL connection.
The Telstra unit was DSL-capable, so we used it — but it was also second-hand and nobody could vouch for it. We plugged it into several wall ports around the flat and its DSL light stayed off on every one of them. That result is consistent with a broken line, and equally consistent with a broken router. With one unknown device and one unknown line, the test simply does not resolve.
客户家里有两台二手路由器，哪一台都不构成一次干净的测试。
TP-Link 那台直接出局：它里面没有 DSL 调制解调，在电话线接入的服务上，配置得再对也连不上。这一点值得直说，因为二手市场上很多路由器外观上像那么回事，本身就不是为 DSL 线路做的。
Telstra 那台是支持 DSL 的，我们就用它——但它同样是二手的，没有人能担保它是好的。我们把它接到房间里好几个墙内网口上，DSL 灯每一个口都不亮。这个结果既符合「线路坏了」，也同样符合「路由器坏了」。一个未知的设备，加一条未知的线路，这个测试本身就得不出结论。
Router fault or line fault: what tells them apart路由器故障还是线路故障：靠什么分辨
| If the router is the problem如果问题在路由器 | If the line is the problem如果问题在线路 |
|---|
| DSL light on one wall port接某一个墙口时的DSL灯 | Off不亮 | Off不亮 |
| DSL light on the other ports接其他墙口时的DSL灯 | Off — same unit, same result同样不亮，因为是同一台设备 | Off — same line, same result同样不亮，因为是同一条线 |
| With a router you already trust换成一台你信得过的路由器 | Light comes on, you are online灯亮了，网也通了 | Still off, on every port每个口都还是不亮 |
| Who can fix it谁能修 | You, that afternoon你自己，当天就行 | The provider's NBN technician运营商安排的NBN工作人员 |
| What it costs you代价是什么 | A working router一台能用的路由器 | A booking and a wait一次预约加一段等待 |
Where the line was actually broken
线路究竟断在哪一段
Where the line was actually broken线路究竟断在哪一段
Exetel serviceExetel宽带服务
active / 已开通
→
Building comms room楼内机房线路
faulty / 故障
Line fault线路故障
→
In-room wall DSL ports房间墙内DSL口
no sync / 不同步
Line fault线路故障
→
Router路由器
DSL light off / DSL灯不亮
→
Devices设备
no internet / 无法上网
The router was the last thing in this chain to show a symptom and the first thing everyone suspects. In fact it was doing exactly what it should: a DSL router will not light its DSL indicator unless it can sync with a working line on the other end of that wall socket. No sync means nothing to talk to. The break was upstream, in the room's cabling and the building's comms room — neither of which we are permitted to open.在这条链路上，路由器是最后才表现出症状的一环，却是所有人第一个怀疑的对象。事实上它做的完全正确：DSL 路由器只有在墙口另一端能对上一条正常的线路时，DSL 指示灯才会亮。灯不亮，说明根本没有东西可以对话。断点在更上游——房间的墙内线路和楼里的机房，而这两处都不是我们能动的地方。
The second visit, and what it settled
第二趟上门，解决了什么
The next morning we came back with a DSL router we knew worked, and went round every wall port again. Still no sync, anywhere in the flat.
That is the whole point of the return trip. Once a router you trust behaves exactly the same way on every socket, the router is no longer a variable and the fault has to be on the other side of the wall — the room's cabling and the building's comms room. At that point the job stops being something we can fix with equipment and becomes something only the provider can dispatch someone for. We called Exetel from the flat and booked the earliest free NBN technician visit, Thursday morning. Once the line is repaired, getting online is just a matter of configuring the router.
第二天早上，我们带着一台确定能用的 DSL 路由器回来，把每一个墙内网口又走了一遍。整套房子，依旧没有一个口能同步。
这一趟的意义就在这里。当一台你信得过的路由器在每一个口上表现完全一致时，路由器就不再是变量，故障只能在墙的另一边——房间的走线和楼里的机房。到这一步，这件事就不再是我们靠设备能解决的了，只能由运营商派人处理。我们在客户家里打电话给 Exetel，约到了最快的一次 NBN 人员免费上门，时间是周四上午。线路修好之后，剩下的就只是把路由器配置一下就能用网。
Two visits, and why the first one could not finish it两次上门，以及第一趟为什么结不了案
1
Visit 1, evening: arrived without a test router of our own第一次上门（当晚）：身上没带自己的对比路由器
Only second-hand units on site现场只有二手设备
2
Checked what the flat already had — a TP-Link with no DSL modem先看现有设备——一台TP-Link不带DSL调制解调
Not usable on a DSL lineDSL线路上根本用不了
3
Used the second-hand white Telstra unit, which is DSL-capable改用那台支持DSL的二手Telstra白色路由器
Condition unknown本身是否正常未知
4
Plugged it into several wall ports around the flat把它接到房间里多个墙内网口逐个测试
DSL light off on all of them所有口的DSL灯都不亮
5
Could not separate a faulty router from a faulty line无法区分是路由器故障还是墙内线路故障
One unknown, two possible causes一个未知量，两种可能
6
Visit 2, next morning: returned with a known-good DSL router第二次上门（次日上午）：带上自己的DSL路由器再来
Router variable eliminated路由器这个变量被排除
7
Tested every wall DSL port again with it用它把各墙内DSL口再测一遍
Still no sync anywhere依旧全部不同步
8
Called Exetel from the flat现场打电话联系Exetel客服
Free NBN technician, Thursday morning预约周四上午NBN人员免费上门
What to take from this one
这一单值得记住的几点
- A DSL light that never comes on is not a diagnosis, it is a starting point. It says the router cannot sync with anything — not why.
- Testing more wall ports with the same unknown router does not add information. Every port is being judged by the same possibly-faulty device.
- One known-good router is worth more than three unknown ones. If you are borrowing gear to test with, borrow something you have seen working.
- Check that a second-hand router actually has a DSL modem before you buy it for a phone-line service. Plenty of them do not.
- When the fault is in the building's cabling, an NBN technician visit arranged through your provider is normally the free path. Ask for it rather than paying to have someone poke at your room.
- Older apartment blocks in Sydney see more of these line faults, and DSL speeds are capped anyway. It is a fair question to ask about a building before you sign a lease.
- DSL 灯一直不亮不是诊断结论，只是排查的起点。它只说明路由器同步不上任何东西，不说明为什么。
- 拿同一台来路不明的路由器多测几个墙口，并不会增加信息量——每个口都是被同一台可能坏了的设备判断的。
- 一台确定是好的路由器，比三台不确定的更有用。要借设备来测，就借一台你亲眼见它正常工作过的。
- 买二手路由器接电话线服务前，先确认它里面真的有 DSL 调制解调。不带的相当多。
- 故障落在楼内线路上时，通过运营商安排 NBN 人员上门通常是免费的那条路。先去问这条路，别急着自己花钱找人来房间里翻。
- 悉尼的老小区遇到这类线路故障的概率更高，DSL 的速度本身也有上限。签租约之前，这是一个值得先问清楚的问题。
Result最终结果
With a known-good DSL router on every wall port and still no sync anywhere, the fault was confirmed as the room's cabling and the building's comms room rather than any equipment in the flat. We called Exetel from the property and booked the earliest free NBN technician visit for Thursday morning; once that line work is done, the connection only needs the router configured.
用一台确定正常的 DSL 路由器把每个墙内网口都测过、依旧全部无法同步之后，故障被确认在房间墙内线路与楼内机房，而不是屋里的任何一台设备。我们在客户家里致电 Exetel，约到最快的一次 NBN 人员免费上门，时间是周四上午；线路处理完之后，把路由器配置一下即可联网。