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Deco bug: Deco is assigning a wired device to a satellite Deco and throughput plummets

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Deco bug: Deco is assigning a wired device to a satellite Deco and throughput plummets

This thread has been locked for further replies. You can start a new thread to share your ideas or ask questions.
Deco bug: Deco is assigning a wired device to a satellite Deco and throughput plummets
Deco bug: Deco is assigning a wired device to a satellite Deco and throughput plummets
2021-01-02 06:51:41
Model: Deco M5  
Hardware Version: V1
Firmware Version: 1.5.1 Build 20201022

Wired throughput can plummet if a wired device gets assigned to a Deco that isn't directly connected to the internet. This seems to be a Deco bug with an easy repro.

 

Consider the following configuration: a computer and two Deco M5s are all attached via Ethernet to the same switch (the Decos are wired to allow wired backhaul). One of the Decos (let's call it 'Main') is also connected to the Internet and is acting in Router mode. In this situation, NO wireless connectivity is being used. Here is a diagram:

 

---
|S|---------- Computer
|W|---------- Deco M5 "Satellite"
|I|---------- Deco M5 "Main"  --------------- CableModem ---------- Internet
|T|
|C|
|H|
---

If you look in the app (tap the big "Internet" button to see the Deco devices, then tap "Main"), you will see "Computer" listed there. Note that there is ONLY a WIRED connection between Computer and Main. WiFi on "Computer" is turned off.

 

The internet connection is 1Gbps. If I test the internet speed with the Deco app, I get about 900Mbps which is great. If I test the internet speed from "Computer", I get about the same -- also great.

 

Now unplug & restart "Main" Deco M5. Of course, "Computer" loses connection but after Main reboots, internet connectivity is restored but "Computer" now appears as managed by "Satellite" Deco M5 (as reported in the list of devices in the app under Internet / Satellite).

 

Now the download speed tested from Computer is about 250Mbps and it stays that way. Download speed tested via the Deco app is still 900Mbps.

 

If I unplug Satellite, sure enough Computer cannot access the internet (which is *really* surprising since the routing tables have not changed and nor has the ARP table and "Computer" is clearly using "Main" as its router). I seriously suspect that when "Computer" is associated with the "Satellite" Deco, data is going to Main then to Satellite then back to Main then out to the internet! Eventually, with Satellite unplugged, "Computer" gets reassigned to "Main" and high throughput to "Computer" is restored. 

 

I cannot find a way to force a specific wired device (or all of them) to be associated with the Main Deco unit. Is there a way to do it? Or another way around this issue?

 

Also, since this looks like a Deco bug to me, is this the right place to report a bug? Does tech support monitor these posts?

 

Thanks,

-JohnnyQ.

 

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#1
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3 Reply
Re:Deco bug: Deco is assigning a wired device to a satellite Deco and throughput plummets
2021-01-03 09:40:40

@JohnnyQ 

Hi, thank you very much for your kind feedback.

We would report your case to the senior engineers for further test.

At the same time, could you please help me check the following details:

1. What is the model number of the switch?

2. How did you make the computer switch back to the connection of the main Deco eventually when it was connected to the satellite Deco?

3. Are you able to reproduce the same problem every time?

 

Thank you very much for your time and patience.

Wait for your reply.

 

 

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#2
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Re:Deco bug: Deco is assigning a wired device to a satellite Deco and throughput plummets
2021-01-03 12:20:51

@TP-Link I don't seem able to reproduce this issue anymore yet I did it 4 times in a row when I was encountering the problem ... and I was *really* careful on the last one. I have a possible partial-explanation for why it may have been happening but I don't think it explains all behaviour. The layout was slightly more complex as shown below:

 

---
|S|---------- Computer
|W|---------- Deco M5 "Satellite"
|1|
---
 |
 |
 |
 *
---
|S|---------- Deco M5 "Main" --------------- CableModem ---------- Internet 
|W|
|2|
---

I *think* the connection between SW1 and SW2 may have been flakey at times (the clip at the end of the ethernet cable labeled with '*' is broken/missing). If the connection between SW1 and SW2 severed then "Computer" would go via WiFi backhaul to "Main" then to the internet. It doesn't explain why *just* rebooting "Main" would change access from fast to slow and stay that way. Certainly for a couple of trials, rebooting "Main" would have been very unlikely to affect the connection between SW1 and SW2.

 

I have tried to repro it several more times now and I cannot. Let's consider it user error unless it recurs. For completeness, here are some answers to your questions:

 

SW1: TrendNet TEG-580G v1.0R

SW2: D-Link DGS-1008D Ver: E1

 

I cannot say with certainty what caused "Computer" to switch back to the "Main" Deco. I would unplug "Satellite's" network, reboot "Satellite", etc.

 

Thanks for having taken the time to look into the issue & sorry that it might just be user error & a bad connection.

 

Regards,

JohnnyQ

 

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#3
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Re:Deco bug: Deco is assigning a wired device to a satellite Deco and throughput plummets
2021-01-04 03:11:23

@JohnnyQ 

Thanks a lot for sharing as well.

Later if it occurred again, please feel free to update this post.

Thank you very much and wish you a happy new year.

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