3G Modem flashing blue light, but no router reconnect

I have experienced this issue now over a variety of modems, routers and mobile networks.

For some reason the PPP session is disconnected and the modem sits with a flashing blue light, showing that it is apparently connected to the mobile network, but will not respond to the routers attempts to initiate a reconnect.

It's almost as if the modem gets into some state, where it does not respond to serial communications on the USB port from the router anymore.

So far, I have seen this happen at completely random intervals at different geographical locations, over the last few months, with the following combinations of routers, modems and networks:

Routers:
TP-LINK MR3420, 3220
Tenda 3116R
MikroTik RB751U (recently)

Modems:
Huawei E220
Huawei E173
Huawei E367
Huawei K3765
Huawei K4605
ZTE MF190 (indicator flashes slow green normally when PPP session is connected, opposite to others)

Networks:
Vodacom
Cell C
8ta

On occasion, I have had the modem indicator light remain on solid blue or cyan, but no internet communication.

Almost all of the times this happens, the router is unable to communicate with the modem if I try to force a disconnect or reconnect. The MikroTik for example pops up a warning "modem did not respond" and attempts to send it serial commands fail.

I have found that not even a soft reboot of any of the routers resolves this condition, as none of them remove USB port power to the modem on reboot.

Only way to fix has been either unplug the modem and plug it in again, or power cycle the router.

If you experience this phenomenon, please share your modem, router and network combination.
Maybe there is some pattern to this?

Same issue

Routers:
TP-LINK MR3220
Netgear MBRN3000

Modems:
Huawei E1752
ZTE K4505-Z

Networks:
Cell C
Vodacom

Base122 said:

Modems:
Huawei E220
Huawei E173
Huawei E367
Huawei K3765
Huawei K4605
ZTE MF190

Click to expand...

:wtf::wtf::wtf:
WTF - Lookout Jola theres someone with more modems than you!
I thought i was a nutcase having 3

Tun@ said:

:wtf::wtf::wtf:
WTF - Lookout Jola theres someone with more modems than you!
I thought i was a nutcase having 3

Click to expand...

Modems:
Huawei E220 - mine
Huawei E173 - borrowed
Huawei E367 - mine
Huawei K3765 - mine
Huawei K4605 - borrowed
ZTE MF190 - mine

.....see not so bad after all...

Base122 said:

For some reason the PPP session is disconnected and the modem sits with a flashing blue light, showing that it is apparently connected to the mobile network, but will not respond to the routers attempts to initiate a reconnect. ]...]
On occasion, I have had the modem indicator light remain on solid blue or cyan, but no internet communication.

Click to expand...

This is confusing, as the only steady (solid) light indicate active PPP connection:
steady blue/cyan - 3G
steady gren -2G

Blinking slow (single flash every 1-3 second) means modem is disconnected (no PPP connection), but is registered (and connected) in terms of network requirements, so it can send/receive USSD, SMS, calls or initiate data connection.

The same with ZTE modems. The only difference with ZTE modems is a red light indicating error condition (by example no SIM in the socket).

sajunky said:

This is confusing, as the only steady (solid) light indicate active PPP connection:
steady blue/cyan - 3G
steady gren -2G

Blinking slow (single flash every 1-3 second) means modem is disconnected (no PPP connection), but is registered (and connected) in terms of network requirements, so it can send/receive USSD, SMS, calls or initiate data connection.

The same with ZTE modems. The only difference with ZTE modems is a red light indicating error condition (by example no SIM in the socket).

Click to expand...

At the moment, I am looking at my MikroTik dual 3G wan setup, with the 8ta E367 (steady blue indicator) and the Cell C white stick ZTE MF190 (green circular indicator flashing 2 seconds on/2 seconds off). Both wan link PPP sessions are active and working normally.

The ZTE MF190 indicator is different from the rest, in that when you plug it in, the indicator is red before it registers on the network, then steady green when registered (presumably 3G) and then blinking green when PPP connected.

I had my Tenda 3116 + K4605 + Vodacom test setup fail last night around 12:45am and happened to see it at the time.
The K4605 normal steady blue light suddenly went off and then after a few seconds started to flash green and then a few more seconds later, flash blue slowly (once every 3 seconds or so).

I left it overnight to see if it would reconnect, but it didn't.
I soft rebooted the Tenda router, but the modem still remained slow flashing blue indicator and the Tenda status page shows "connecting".

This symptom is the same as I have encountered many times now, where it seems the modem is in some state that the router will not communicate with it anymore, or it simply does not want to respond to a command to start the PPP session, even though it appears to be registered on the network. (or is it actually?) The Tenda router has no other tools to try and send USSD, SMS etc. so cannot check.

A power cycle reboot has sorted it out and it is now working again.
Also, sometimes, simply unplugging the modem and plugging it in again, sorts the problem out.

Always seems to be that the power to the modem must be removed, in order to recover from this condition.

Base122 said:

At the moment, I am looking at my MikroTik dual 3G wan setup, with the 8ta E367 (steady blue indicator) and the Cell C white stick ZTE MF190 (green circular indicator flashing 2 seconds on/2 seconds off). Both wan link PPP sessions are active and working normally.

Click to expand...

I am pretty sure of these lights. ZTE single flash means modem is registered to the network, but PPP connection not active. It is why I think something is wrong with router indicators (logs - whatever).

Base122 said:

The ZTE MF190 indicator is different from the rest, in that when you plug it in, the indicator is red before it registers on the network, then steady green when registered (presumably 3G) and then blinking green when PPP connected.

Click to expand...

It differs only with red light. I have ZTE Vodafone K3570, but all ZTE should behave the same. I noticed sometime ago red light on the startup, not sure - searching for network (similar to Huawei double green flash). Red light is not mentioned in modem manual. The rest is identical to Huawei. If it goes steady green, it means it is registered (and PPP connected) to 2G, not 3G, this is for sure.

Base122 said:

I had my Tenda 3116 + K4605 + Vodacom test setup fail last night around 12:45am and happened to see it at the time.
The K4605 normal steady blue light suddenly went off and then after a few seconds started to flash green and then a few more seconds later, flash blue slowly (once every 3 seconds or so).

Click to expand...

It was PPP connected, then (if double green flash) it lost 3G signal completely. Then it re-registered to 3G network, but PPP connection gone.

Base122 said:

I left it overnight to see if it would reconnect, but it didn't.
I soft rebooted the Tenda router, but the modem still remained slow flashing blue indicator and the Tenda status page shows "connecting".

This symptom is the same as I have encountered many times now, where it seems the modem is in some state that the router will not communicate with it anymore, or it simply does not want to respond to a command to start the PPP session, even though it appears to be registered on the network. (or is it actually?)

Click to expand...

It is either that modem is registered to 3G network, or it was the last state before hanging. Or modem is simply in intermediate command state due to miss-issued commands by the router. There is communication problem between router and modem for sure.

Have a situation at the moment on a MikroTik RB751U dual 3G wan remote site.
Wan1 using a Huawei E173 on Vodacom has gone down.

Luckily I can still access the router on wan2 (8ta)

The wan1 PPP link status is constantly cycling between "reseting link", "initializing modem" and "disconnected".

The router is able to communicate with the E173 on the info channel(3) to show this information:
(Signal not too good at -91 dBm, but I doubt that's the reason for the problem)



The router is communicating with the E173 on the data channel (0) in this case.
Even though it is responding to "AT" commands, it does not establish a PPP session.





Tried disabling and enabling the PPP connection several times. - no change
Rebooting the router remotely does not help either.

Pretty sure the symptom is the same with a blue flashing indicator, but will have to drive to the site later to be sure.

It's a pity that rebooting the router does not remove power from the USB port, as I am sure that would have helped to recover from this situation.

***Mmmm...this has now got me thinking of a way to somehow interrupt the USB port power on a router reboot....

Base122 said:

Tried disabling and enabling the PPP connection several times. - no change
Rebooting the router remotely does not help either.

Pretty sure the symptom is the same with a blue flashing indicator, but will have to drive to the site later to be sure.

It's a pity that rebooting the router does not remove power from the USB port, as I am sure that would have helped to recover from this situation.

***Mmmm...this has now got me thinking of a way to somehow interrupt the USB port power on a router reboot....

Click to expand...

I wonder if its possible to fix the problem with AT commands; either de-registering from the network and registering again, or turning the radios of and on again, or even resetting the modem.

ginggs said:

I wonder if its possible to fix the problem with AT commands; either de-registering from the network and registering again, or turning the radios of and on again, or even resetting the modem.

Click to expand...

Would be great if a magic AT command could be found!

Otherwise I am thinking a ULN2003 driven from some TTL point on the routerboard, inserted in the USB power line....(there goes the warranty!)

Basically, when that TTL point goes low during a reboot cycle, the ULN2003 would shut off and the power to the USB port would be interrupted until it goes high again and switches on.

Hopefully such a point would remain high while the router is operating normally.

Or maybe some completely external idea using an optical sensor on one of the routerboard LED's to control USB port power...

All my fiddling remotely seems to have messed up the wan2 link on the site now as well, so I guess I'll be driving over there sooner than I planned **MUST FIND A SOLUTION!!**

Base122 said:

Would be great if a magic AT command could be found!

Click to expand...

Want to give me a login to your router?

ginggs said:

Want to give me a login to your router?

Click to expand...

Might be an idea.
I will probably end up having to reset at the other side now anyway and it could be days before this problem shows up again.
Will let you know.

**Edit:
Although, thinking about this again, on most of the previous times this has happened, the RB751 has been unable to communicate with the modem and returned a "modem not responding" error.
Under those conditions, an AT command solution would be no good. USB power interrupt would probably be the only solution.

I think this is the first time I have noticed it was actually still communicating on the serial port.

Maybe the indicator is flashing differently?
I will establish that later after going out to take a look.

Maybe the indicator is flashing differently?
I will establish that later after going out to take a look.

Click to expand...

So I get to the site and as expected the indicator on the E173 is flashing blue.
Switched on async debugging on the RB751U and can see the router communicating with the modem, which is responding to AT commands. However, it simply will not respond to the commands to connect a PPP session.

I tried some of ginggs AT+CFUN commands suggested in another thread.

AT
OK

AT+CFUN?
+CFUN: 1

Looks normal so far, but still will not connect.

AT+CFUN=4 (switch off tx and rx RF circuits)
OK

E173 indicator now flashes green twice every three seconds.

Try to switch on RF again:
AT+CFUN=1
ERROR

Then tried:
AT+CFUN=6
OK

After a few seconds the indicator starts flashing blue again.
Then I enabled the PPP connection and amazingly it connected!

So it seems like the AT+CFUN=4, AT+CFUN=6 sequence was able to recover this condition.

Then tried putting the sequence AT+CFUN=4;AT+CFUN=6 in the PPP connection modem initialization string, thinking I would just get the modem to perform this sequence by default each time.

Unfortunately this didn't work.
The modem responds to the command sequence, by starting to flash green twice every three seconds and then blue.
But, I think it is some timing issue, as the MikroTik doesn't wait long enough after sending the modem initialization, before it starts trying to connect. It seems to try to connect before the modem is actually ready, fails and then starts from scratch by sending the initialization string again and the whole cycle repeats.

Pity, as this might have helped solve the problem.

Maybe if there was a way to send serial commands to the modem via scripting, something could be done. The manual terminal approach is not practical for a remote site.
It seems like this is a bit of a problem issue for the RB751. There is discussion around sending AT commands with scripting, but haven't found anyone able to do so yet.

Regarding this modem not responding issue, I did find this on the MikroTik forum:
http://forum.mikrotik.com/viewtopic.php?f=9&t=56463

Seems like this is a bit of a problem for others too, as USB power cannot be turned off on the RB751U.
I still think cycling the power on the USB port during a reboot cycle, is the best way to go.

Even shutting down the RB751 with the "Shutdown" command still does not remove USB port power.

Just a heads up as to why my wan2 link had also gone down during my problem situation on my dual 3G wan setup.....

wan2 uses 8ta.

I have an airtime balance of R43 and had previously bought a R40 100MB data bundle.
This bundle expired during my testing.

8ta does not then simply go over to using data from you normal airtime balance.
Effectively, you get cut off from the internet and directed to an 8ta web page where you must consent to going out of bundle, before you have to reconnect your data session and then continue normally.

A nice idea to "protect" the customer from the OOB shark, but no good for my application.
Doesn't seem to matter how big your airtime balance is, you cannot continue using data until you consent.

If you don't buy any bundles and use data at R1.00 per MB, then there is no problem.

Lesson learned....

Is it still problem if you register on https://onnet.8ta.com, so you can access by login/password from remote location and purchase the bundle on the site?

Have registered the 8ta number on the website.
Bought another 100MB bundle.
Will see what happens when this expires.

Hopefully I will just be able to buy another bundle and continue, or be able to get past the consent page remotely somehow.

Will be a while before the 100MB gets used up though, as the 8ta link is not the primary link for the site.

Base122 said:

I have experienced this issue now over a variety of modems, routers and mobile networks.

For some reason the PPP session is disconnected and the modem sits with a flashing blue light, showing that it is apparently connected to the mobile network, but will not respond to the routers attempts to initiate a reconnect.

It's almost as if the modem gets into some state, where it does not respond to serial communications on the USB port from the router anymore.

So far, I have seen this happen at completely random intervals at different geographical locations, over the last few months, with the following combinations of routers, modems and networks:

Routers:
TP-LINK MR3420, 3220
Tenda 3116R
MikroTik RB751U (recently)

Modems:
Huawei E220
Huawei E173
Huawei E367
Huawei K3765
Huawei K4605
ZTE MF190 (indicator flashes slow green normally when PPP session is connected, opposite to others)

Networks:
Vodacom
Cell C
8ta

On occasion, I have had the modem indicator light remain on solid blue or cyan, but no internet communication.

Almost all of the times this happens, the router is unable to communicate with the modem if I try to force a disconnect or reconnect. The MikroTik for example pops up a warning "modem did not respond" and attempts to send it serial commands fail.

I have found that not even a soft reboot of any of the routers resolves this condition, as none of them remove USB port power to the modem on reboot.

Only way to fix has been either unplug the modem and plug it in again, or power cycle the router.

If you experience this phenomenon, please share your modem, router and network combination.
Maybe there is some pattern to this?

Click to expand...

are you plugging the usb modem directly into the router or using extention usb male 2 female. i found my e1820 behaving like yours with extention, but plugged in directly it connects.

S.T.A.L.K.E.R said:

are you plugging the usb modem directly into the router or using extention usb male 2 female. i found my e1820 behaving like yours with extention, but plugged in directly it connects.

Click to expand...

Sometimes with a short extension, sometimes not.
Sometimes on a powered USB hub or normal non powered as well.

Doesn't seem to make a difference to this problem.
Modem seems to get into some state, where it will not respond to the routers normal attempts to get it to reconnect.

If you look at the "MikroTik RouterBoard and 3G modems thread", I have come up with a MikroTik script using ginggs AT reset sequence suggestion, to see if this problem can be resolved.

Now just have to wait for it to happen again.

I am getting this problem...from what i can tell.
Seems the same.

Huawei E367
TP-LINK M3020


....sigh


I have to usually pull power and hope for a propper connect after that.
It worked this morning no problem for 4 solid hours but i left the house for about 2 hours at lunch time and when i got back i have been struggling ever since. Stuck the modem back into my laptop.

Sometimes i get a solid light blue light and the router control panel tells me its connected but no response from browsers.
sometimes it gets stuck on solid green and wont connect.
sometimes its connected and goes solid green and it still says its connected but get no respnse from browser.

gutted...to say the least.

I just tried flashing the E367 with the 11.810.09.20.00 firmware to no effect.


shoot me now.

You was connecting non-original power unit to the router. Do you still use long (non original) USB power cable between (now original) charger and router?

Your posts are here:
http://mybroadband.co.za/vb/showthread.php/273744-Routers-to-use-with-3G-HSPA-Modems/page85