I connected a mobile usb modem to a rb751g with the intention that the router should provide network access for some laptops. It worked great... for two days. Within a week the mobile connection has failed 4 times, in 4 different ways. Has anyone experienced anything similar? Any suggestions on how to make it stable?

ROS: 5.20

Heres the code I used to configure the interface So when it stopped working, the messages showing in the log are:

echo: async,ppp,info ppp-out1: initializing...
echo: async,ppp,info ppp-out1: reseting link...
echo: async,ppp,info ppp-out1: reseting link... - could not acquire serial port
echo: async,ppp,info ppp-out1: disconnected

I rebooted the router - to no help.
I disconnect the usb, wait a minute and reconnect ... still no help
Then I unplug the power of the router for a minute - and it starts working again

Then the next day it stops working again. From experience from the day before I unplug the power from the router and reconnect the power - to no help. Then I tried unplugging and reconnect the usb - still no help. Finally I deleted the interface and recreated it using the same command, and it started to work again.

A couple of days later it stopped working again.
I tried all the tricks mentioned above, and when I tried to recreate the interface, it failed. It turns out that the port is no longer named usb1, but usb3. So I edit the command, recreate the interface and it works again.

But just a couple of hours later it stops again. Before doing anything else, I check the usb status. It turns out that the port once again has changed, now back to start and it's called usb1 again.
So I change the port of the existing interface from usb3 to usb1 - to no help.
Then I deleted the interface and recreated it - to no help.
Rebooted the router - to no help.
Disconnected and reconnected usb - to no help.
Disconnected the power and reconnected - then it started working.

How can I make this stable?

*bump*

Max. current defined by USB standard is 500mA per port.
From my experience some 3G modems do not respect this standard.
This is the reason RB's USB controller sometimes cut off the output power.
Try to connect your modem using USB power injector (http://routerboard.com/5VUSB)
and external power supply (5V, 1A).

HTH,

Thank you. I'll give that a try.

you can try to lower the output power for the wireless card.
Make sure that you use the latest RouterOS version.
Are you using USB cable between the modem and the board? We suggest to connect the modem directly to the board.

I was not using any cable between modem and card.
Where do I find the settings to adjust usb power?

Now I've tested with a usb-power inejctor (huawei brand, not mikrotik) and it has been somewhat more stable. More stable in the sense that I did not need to change the router configuration. Disconnecting and reconnecting the routers power has solved the problem when the card has stopped working. Note that I did not need to disconnect the usb power injector. So the modem did not need power off, just the RB. Also, rebooting the RB did not help. It has to have the power disconnected/reconnected.

Edit:
Ah, maybe you where talking about the wlan tx power? (Presumably to reduce the box total power consummation.)

Ah, maybe you where talking about the wlan tx power? (Presumably to reduce the box total power consummation.)

Yes, correctly.

With the reduced wlan tx-power the usb was alive for almost 2 weeks!
That is, the day after I lowered the power I left for 11 days. When I got back, it was still working - and it stopped working during that day. I'm not sure if is improvement though. It managed 2 days of use and 9 days of idling.

I'm starting to think this is not power related. Anyone got ideas for what else it could be?