Community discussions

MikroTik App
 
dermawas
newbie
Topic Author
Posts: 46
Joined: Sat Jul 10, 2021 7:06 am

when using 3g USBModem - router was rebooted without proper shutdown by watchdog timer

Tue Jan 25, 2022 12:08 pm

Hi all,

please help to review my router (RB750GR3) config.
i notice this because my main ISP is down, and i have sierra 3g USB modem, that i usually connect for sending sms but when such incident (main isp down) . i configured this modem for back up internet.

here is the weird thing,
when i change to USB 3G Modem, the router rebooted several time as this photo shown
WhatsApp Image 2022-01-25 at 5.06.14 PM.jpeg
i've attached the export files, is there something wrong with my config that causes the router to reboot several time ?
Thank you
You do not have the required permissions to view the files attached to this post.
 
mkx
Forum Guru
Forum Guru
Posts: 7671
Joined: Thu Mar 03, 2016 10:23 pm

Re: when using 3g USBModem - router was rebooted without proper shutdown by watchdog timer

Tue Jan 25, 2022 12:31 pm

One possibility is that your 3G modem draws too high current and RB750GR3 is not able to sustain it, quite a few of them come with sort of a Y-cable and one branch is used expressly to pick up extra current from another USB port.

You could try to get a powered USB hub and plug it between router and dongle. This way hub's power adapter will supply power to dongle.
BR,
Metod
 
Zacharias
Forum Guru
Forum Guru
Posts: 3272
Joined: Tue Dec 12, 2017 12:58 am
Location: Greece

Re: when using 3g USBModem - router was rebooted without proper shutdown by watchdog timer

Tue Jan 25, 2022 12:35 pm

Supported modems here https://help.mikrotik.com/docs/display/ ... ularmodems
Your device most obviously goes unresponsive for a minute, so watchdog has to reboot it...
 
dermawas
newbie
Topic Author
Posts: 46
Joined: Sat Jul 10, 2021 7:06 am

Re: when using 3g USBModem - router was rebooted without proper shutdown by watchdog timer

Tue Jan 25, 2022 1:32 pm

Supported modems here https://help.mikrotik.com/docs/display/ ... ularmodems
Your device most obviously goes unresponsive for a minute, so watchdog has to reboot it...
yeah the modem is not part of the supported list. but i think this sierra 885 is compatible tho, since i saw the setting how to make it works in this forum.
i would love to know what caused the unresponsiveness, but there is no output generated by the watchdog.
One possibility is that your 3G modem draws too high current and RB750GR3 is not able to sustain it, quite a few of them come with sort of a Y-cable and one branch is used expressly to pick up extra current from another USB port.

You could try to get a powered USB hub and plug it between router and dongle. This way hub's power adapter will supply power to dongle.
could be, but i was opening winbox all the time and watch the curent, temp, memory & cpu when it got hang, there is nothing that suggest sudden voltage drop.
the interface window packet just suddenly stop moving and not long the router rebooted.
 
mkx
Forum Guru
Forum Guru
Posts: 7671
Joined: Thu Mar 03, 2016 10:23 pm

Re: when using 3g USBModem - router was rebooted without proper shutdown by watchdog timer

Tue Jan 25, 2022 2:13 pm

You could try to get a powered USB hub and plug it between router and dongle. This way hub's power adapter will supply power to dongle.
could be, but i was opening winbox all the time and watch the curent, temp, memory & cpu when it got hang, there is nothing that suggest sudden voltage drop.
the interface window packet just suddenly stop moving and not long the router rebooted.
If what I wrote is the reason, then you won't see it coming on the usual health sensors. The thing is that one of two most power-demanding things in wireless modem is radio transmitter (the other is CPU/DSP processing both directions) and radio transmitters can use quite high powers ... specially if they are not really power-optimized (which is the case with earlier models for each mobile generation, 3G is no exception) ... 3G devices are generally allowed to transmit with 200mW - on the antenna. Given the inefficiency of output stage (power amplifier), actual power draw can be upwards from 1W ... and 1W for USB-powered devices is really a lot (USB 2.0 standard specifies max power draw to be 500mA @ 5V = 2,5W). If internal design of a board offering USB port is not smartly done, then excessive power draw over USB port can mean drop of voltage used by other components ...

But it's up to you whether to pursue my suggestion or not, I'm giving it to you for free :wink:
BR,
Metod
 
dermawas
newbie
Topic Author
Posts: 46
Joined: Sat Jul 10, 2021 7:06 am

Re: when using 3g USBModem - router was rebooted without proper shutdown by watchdog timer

Tue Jan 25, 2022 4:29 pm


could be, but i was opening winbox all the time and watch the curent, temp, memory & cpu when it got hang, there is nothing that suggest sudden voltage drop.
the interface window packet just suddenly stop moving and not long the router rebooted.
If what I wrote is the reason, then you won't see it coming on the usual health sensors. The thing is that one of two most power-demanding things in wireless modem is radio transmitter (the other is CPU/DSP processing both directions) and radio transmitters can use quite high powers ... specially if they are not really power-optimized (which is the case with earlier models for each mobile generation, 3G is no exception) ... 3G devices are generally allowed to transmit with 200mW - on the antenna. Given the inefficiency of output stage (power amplifier), actual power draw can be upwards from 1W ... and 1W for USB-powered devices is really a lot (USB 2.0 standard specifies max power draw to be 500mA @ 5V = 2,5W). If internal design of a board offering USB port is not smartly done, then excessive power draw over USB port can mean drop of voltage used by other components ...

But it's up to you whether to pursue my suggestion or not, I'm giving it to you for free :wink:
ok, thank you for the suggestion, I'll give it a shot for this powered USB extension. need to shop around for it. :D

will post if this fixed the rebooting
 
dermawas
newbie
Topic Author
Posts: 46
Joined: Sat Jul 10, 2021 7:06 am

Re: when using 3g USBModem - router was rebooted without proper shutdown by watchdog timer

Sun Mar 13, 2022 1:22 pm

I got the powered USB HUB.
but somehow it wouldn't connect to the 3g connection now.
so i can't reproduce the restarting event. will try to figure out a way to connect to internet using 3g and will update on the progress

Who is online

Users browsing this forum: Bing [Bot], thefelix, washdogg87 and 27 guests