DECO X75 can't boot correctly after power cut off in house.

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DECO X75 can't boot correctly after power cut off in house.

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DECO X75 can't boot correctly after power cut off in house.
DECO X75 can't boot correctly after power cut off in house.
2023-11-24 18:03:08 - last edited 2023-11-27 14:18:22
Model: Deco X75  
Hardware Version: V1
Firmware Version: 1.2.8 Build 20230901 Rel 36505

Hi friends, I've experienced an strange issue, but I'm a bit worried because the way to fix it, was to reinstall all my DECO X75 units again.

I'm using a Router from my ISP Provider, which is connected to an ONT device by using RJ45 to get fiber connectivity.

Today I had a power cut off in my home. As soon the power at home came back all devices including the ISP router started to boot up. My ISP Routers takes long to boot up, maybe two minutes or even a bit more some times. As a result the X75 units were with the Red Light fixed. Once the ISP Router was ready and booted up, I waited a couple minutes for the Deco X75 Units to check if they were be able to setup correctly. Unfortunately nothings changed and the green light never turned on.
The X75 main unit was able to start the wireless lan, so from my mobile phone I was able to connect to the WiFi, but there was not gateway available to use internet. I checked my TCP/IP settings in my iPhone, and I could check the local IP provided to my phone (192.168.68.XX) was in the common range when you setup your X75 Units as Router Wifi, and not as Access Point ( which it is my case ), which usually takes a Dynamic IP from your DHCP, which in my case coming from my ISP Router.
So I could confirm then, my main Deco Unit was setup with a different configuration that I did.
After some reboots, and switch off of the rest of deco unitys, nothing worked.
So finally I had to create a new network, add the main X75 unit as Router Wifi, then change it to Access Point mode, and then turned on the rest of the Deco Units, and I waited for them to autoconfigure.

So I'm really worried about this behaviour because where I'm living is very common from time to time, this kind of power cuts issue.

Can you give me some kind of explanation about why this can happen?

Thanks.

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#1
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Re:DECO X75 can't boot correctly after power cut off in house.-Solution
2023-11-24 21:31:23 - last edited 2023-11-27 14:18:22

  @latas2002 

 

To avoid this issue in the future, turn off Smart DHCP feature under Advanced page in Deco app:

 

 

 

 

Even with Smart DHCP enabled, you did not have to reinstall your Deco X75s again. The specific way of restarting Deco mesh and your ISP router after power outage would have recovered Deco mesh. If you'd like to, I can provide the order of restarts. You won't be needing it, if you turn off Smart DHCP.

If you need that order of restarts, tell me what else is wired to Main Deco other than Ethernet cable linking it to ISP Router.

 

Also, it is somewhat known issue that caused somewhat heated feedback to TP-Link Support from people who experienced it. If you have a bit of IT background and are curious, I can explain what actually happened and why, but it'll be in somewhat lengthy way. Which (why did it happen) would not matter much if you turn off that feature, because it won't be triggered again.

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Re:DECO X75 can't boot correctly after power cut off in house.-Solution
2023-11-26 21:34:10 - last edited 2023-11-27 14:18:49

Restart sequence after power outage when Main Deco running in AP mode took over as DHCP server, DNS Server, default gateway.

  1. Power off primary DHCP server (ISP Router) and Main Deco
    Both must be powered off for recovery steps to work.

     
  2. Unplug all Ethernet cables from Main Deco except one linking it to ISP Router
    Main Deco has WAN/LAN ports autosensing. Under some conditions, on restart it could mistakenly consider LAN port to be WAN port. To avoid the possibility of that, just unplug these “other” Ethernet cables.

     
  3. Power off all Satellite Deco, especially important if there are hardwired Satellite Deco
    Deco mesh running in AP mode has undocumented resiliency feature: when Main Deco goes down, hardwired Satellite Deco could silently take over. Which is quite useful for large Deco mesh running in AP mode, with hardwired Satellites, but not in the case when you need to stop Deco from running DHCP service. 

     
  4. Power on ISP Router and wait till it starts its own DHCP service
    If you have device such as PC or laptop or Smart TV hardwired to your LAN not through Main Deco, it would be easy to find when ISP Router is fully operational. In case nothing is hardwired to ISP Router bypassing Main Deco, just wait till lights on ISP Router show its status as fully operational and give another few minutes.

If ISP Router can’t recover on powering on, which is unlikely but mentioning it just in case, this is now not Deco mesh related problem. Deco mesh is powered off. Troubleshooting of ISP Router should follow.
 

  1. Power on Main Deco
    Main Deco should start in AP mode, as configured, and should not run its own DHCP service because it sees DHCP service active from ISP Router. Check in Deco app that Main Deco is online and with IP address it received from ISP Router withing ISP Router configured IP range.

     
  2. Power on Satellite Decos
    After Main Deco is online, you can power on Satellite Decos in any order.

     
  3. Plug Ethernet cables back to Main Deco that were unplugged earlier.
    You have recovered your home network to its correct state.
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Re:DECO X75 can't boot correctly after power cut off in house.-Solution
2023-11-24 21:31:23 - last edited 2023-11-27 14:18:22

  @latas2002 

 

To avoid this issue in the future, turn off Smart DHCP feature under Advanced page in Deco app:

 

 

 

 

Even with Smart DHCP enabled, you did not have to reinstall your Deco X75s again. The specific way of restarting Deco mesh and your ISP router after power outage would have recovered Deco mesh. If you'd like to, I can provide the order of restarts. You won't be needing it, if you turn off Smart DHCP.

If you need that order of restarts, tell me what else is wired to Main Deco other than Ethernet cable linking it to ISP Router.

 

Also, it is somewhat known issue that caused somewhat heated feedback to TP-Link Support from people who experienced it. If you have a bit of IT background and are curious, I can explain what actually happened and why, but it'll be in somewhat lengthy way. Which (why did it happen) would not matter much if you turn off that feature, because it won't be triggered again.

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Re:DECO X75 can't boot correctly after power cut off in house.
2023-11-26 02:50:05

  @Alexandre. 

Hi Alexandre, and thanks for your feedback. I followed your instructions, and it was a bit weired. Even Smart DHCP looked to be disabled, I touched the button and a next window open, where the switch button was in fact enabled. I turned it off.

I'm a technical expert in development and programming, and I'm very familiar with networking since a lot of years ago, so I thank you a lot if you want to give me further information about what has happened here.

 

Thanks for your support.

 

Best regards.

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Re:DECO X75 can't boot correctly after power cut off in house.
2023-11-26 06:27:06

  @latas2002 Did you verify via the app that  Deco Unit was setup with a different configuration that you did?  Or did you just observe it was acting as a DHCP server when disconnected from Internet?

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Re:DECO X75 can't boot correctly after power cut off in house.
2023-11-26 21:00:35 - last edited 2023-11-26 22:24:48

  @latas2002 

 

I am going to tell you a story about system design decisions, which are foolproof and could not possibly go wrong … until taken from development/staging to production environment/real life - and do go wrong. If you have IT knowledge and experience in software development, that situation should be familiar to you.

When Main Deco runs in Access Point mode, it still has all router software code. When primary DHCP server in LAN goes down, and in home network that usually means ISP Router went down, Main Deco will take over. Main Deco will become the default gateway, DHCP server and DNS server. Why? Because it can, apparently.

Main Deco does it in a smart way, actually: as long as it runs undisturbed it will provide IP addresses in the same range as were previously configured in ISP Router. Devices already known to Deco mesh, when they renew their IP address, they’ll get the same IP address they have now from Main Deco DHCP service.

This is smart functionality that aims at having home network operational even when primary DHCP server is down. Also, completely unnecessary for a regular home network. In my household, for example, when ISP Router goes down nobody cares if they can still print on network printer or if automatic PC backups to backup server run uninterrupted. What user at my house would be concerned is she can’t view online cartoons on her tablet.

If you bounce Main Deco while ISP Router is down, it creates additional mess: Main Deco resets itself on reboot and starts with default Deco router IP range 192.168.68.*. Devices will be getting IP addresses from that IP range. That’s what happened after power outage you experienced.
Still, that should not be a problem: DHCP lease time from Main Deco is in mere minutes. As soon as ISP Router (primary DHCP server) is back, Main Deco will yield to it and the network should recover promptly.

This is what they call Smart DHCP service: if there is DHCP service active on LAN, I will not start mine. If there is none, I’ll start mine.

In summary: smart design, helps network resiliency, completely harmless, network recovers to its normal state almost immediately after primary DHCP server come online. What could possibly go wrong?

Here comes the proverbial “but:” what would happen if primary DHCP server is also “smart?” Its developers may have thought: “why would we let idiot user start DHCP service from our DHCP server, when other DHCP service is already active? That would only create huge mess.”
For ISP Routers being "smart" is quite unusual, these routers almost always on restart just enable their DHCP service no matter what – thus really promptly recovering home network, taking control back from Deco. Yours is only second time I hear on that forum that is “smart.”
As for standalone DHCP servers, those often come with “smart” functionality. Some allow to turn it off through configuration setting, some don’t. My Synology NAS came with basic DHCP server, I tested it: it is “smart” and there is no option to turn it off. Using it in combination with Deco mesh could cause the same mess on home network you’ve experienced.

Until recently Deco firmware did not have the option to turn off Smart DHCP feature. That caused very heated feedback from people who run their standalone DHCP server with same Smart DHCP functionality and bounce it. During the bounce, Main Deco takes over as DHCP server. After standalone DHCP server comes back, it sees Main Deco running as DHCP server and does not start its own DHCP service. Many hours of troubleshooting could follow…

Nowadays most of new Deco models have firmware that has an option to turn this feature off. For older Deco models where this feature can not be turned off there are workarounds. You can put ISP Router on UPS (Uninterruptible Power Supply) so that it’ll be on while Main Deco reboots during power outage. You can, if there is such configuration option, turn off Smart DHCP feature in standalone DHCP server you are running on your LAN, or in ISP Router.
If nothing else, the specific way of restarting Deco and ISP Router after power outage will recover your home network. I’ll provide restart steps in the next post I make to this forum topic. You may have guessed them already, but there are few gotchas I haven’t mentioned yet.

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Re:DECO X75 can't boot correctly after power cut off in house.-Solution
2023-11-26 21:34:10 - last edited 2023-11-27 14:18:49

Restart sequence after power outage when Main Deco running in AP mode took over as DHCP server, DNS Server, default gateway.

  1. Power off primary DHCP server (ISP Router) and Main Deco
    Both must be powered off for recovery steps to work.

     
  2. Unplug all Ethernet cables from Main Deco except one linking it to ISP Router
    Main Deco has WAN/LAN ports autosensing. Under some conditions, on restart it could mistakenly consider LAN port to be WAN port. To avoid the possibility of that, just unplug these “other” Ethernet cables.

     
  3. Power off all Satellite Deco, especially important if there are hardwired Satellite Deco
    Deco mesh running in AP mode has undocumented resiliency feature: when Main Deco goes down, hardwired Satellite Deco could silently take over. Which is quite useful for large Deco mesh running in AP mode, with hardwired Satellites, but not in the case when you need to stop Deco from running DHCP service. 

     
  4. Power on ISP Router and wait till it starts its own DHCP service
    If you have device such as PC or laptop or Smart TV hardwired to your LAN not through Main Deco, it would be easy to find when ISP Router is fully operational. In case nothing is hardwired to ISP Router bypassing Main Deco, just wait till lights on ISP Router show its status as fully operational and give another few minutes.

If ISP Router can’t recover on powering on, which is unlikely but mentioning it just in case, this is now not Deco mesh related problem. Deco mesh is powered off. Troubleshooting of ISP Router should follow.
 

  1. Power on Main Deco
    Main Deco should start in AP mode, as configured, and should not run its own DHCP service because it sees DHCP service active from ISP Router. Check in Deco app that Main Deco is online and with IP address it received from ISP Router withing ISP Router configured IP range.

     
  2. Power on Satellite Decos
    After Main Deco is online, you can power on Satellite Decos in any order.

     
  3. Plug Ethernet cables back to Main Deco that were unplugged earlier.
    You have recovered your home network to its correct state.
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Re:DECO X75 can't boot correctly after power cut off in house.
2023-11-27 09:50:49

  @Alexandre. 

I assume that, in the scenario you describe, the ISP router detected another active DHCP router because the Deco forgot where was its WAN port, and acted as a DHCP server on that WAN port as well.  This would not occur in case only the ISP router is restarted.

 

I assume also that the Deco remained "red" because it is configured to receive a dynamic IP from the ISP router, hence will remain red until the ISP router acts as a DHCP server.  When configuring the Deco in AP mode, is there a way to configure it with a static IP configuration?  That would allow the Deco to communicate with Internet, become green, and stop its DHCP server.

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Re:DECO X75 can't boot correctly after power cut off in house.
2023-11-27 13:36:29 - last edited 2023-11-27 13:43:10

yves_b wrote

  @Alexandre. 

I assume that, in the scenario you describe, the ISP router detected another active DHCP router because the Deco forgot where was its WAN port, and acted as a DHCP server on that WAN port as well.  This would not occur in case only the ISP router is restarted.

 

  @yves_b 

 

The trigger for the event is DHCP service disappearing from the LAN. That is what forces Main Deco to take over as DHCP server. WAN/LAN port autosensing could only contribute to failure of the recovery process and only under very specific cases.

 

For home networks where DHCP service runs on ISP router, it is enough to restart ISP router to trigger this issue. Every time you restart ISP router, with Deco mesh running in AP mode and Smart DHCP setting enabled, the issue will be triggered. For most people it'll be unnoticed, because after the ISP router restart the network will promptly return to its normal state.

 

If you would like to, I can provide you an example of what device on the network will see as a response to its DHCP query when ISP router is down but Main Deco has not been bounced, and when ISP router is down and Main Deco has been bounced. 

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Re:DECO X75 can't boot correctly after power cut off in house.
2023-11-27 14:17:42

  @Alexandre. 
Ok understood. It makes sense. In fact I've got a Synology NAS 1813+ in my network. I will follow your instructions below for a right boot up if it happens again and turning off DHCP Smart from DECO wouldn't do the trick.

 

Best regards.

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Re:DECO X75 can't boot correctly after power cut off in house.
2023-11-27 14:24:15

  @yves_b It's a timing problem. If you experience a power outage at home, all your devices will try to boot up at same time the power is restored. In my case the ISP router takes long to boot up. It's about 2 minutes. Weird but it is what it is. It's not broken. So in my scenario Deco starts faster. And that was the issue.
 

Cheers.

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Re:DECO X75 can't boot correctly after power cut off in house.
2023-11-27 14:54:21

  @Alexandre. 

 

If the main Deco is not bounced, will it answer to DHCP requests from its WAN port?

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