Verizon Disconnects (MC7455)

[swwifty]

In the last week or so, I've suddenly been having 3 to 4 disconnects or more per day from Verizon. I'm normally connected for weeks at a time without issue. At first, I thought it was my connection monitor resetting the modem when it couldn't ping a few IP addresses. I disabled that, and have found that the modem is still resetting a lot. I'm not sure what's going on here but below is my hardware config:

- Raspberry PI powered via PoE (Powered via a ubiquiti 8-60w switch that normally shows about 5w usage)
- Sierra MC7455 modem in USB enclosure with upgraded USB cable

I'm thinking the issue is maybe not enough power via PoE, or my USB cable is going bad? Below is a screenshot from my system logs from when the modem disconnected/reconnected.

Screenshot from 2019-08-26 20-04-55.png

Any input would be appreciated.

[swwifty]

An update on what I've tried.

I rebooted my entire setup last night to make sure it wasn't something else going on, but I still had 2-3 disconnects over night. I don't think it's a power issue as i'm using about 5w on regular via PoE and can go up to 15w if I need to.

I did change the modem to MBIM mode from QMI mode to see if that helps. Strangely though Verizon connected me to other bands when I did this, so I might have to create a band lock to get back to the faster bands.

I'll report what happens.

[JimHelms]

Inadequate power is one of the major culprits for disconnection issues. And, one of the easiest to troubleshoot (i.e., swap-em-out). It is certainly worth trying since it was once connected without issue.

[swwifty]

Inadequate power is one of the major culprits for disconnection issues. And, one of the easiest to troubleshoot (i.e., swap-em-out). It is certainly worth trying since it was once connected without issue.

what do you recommend swapping out? the USB cable?

[JimHelms]

Do you have a different PoE injector you can try first?

[swwifty]

Do you have a different PoE injector you can try first?

I do have one, but currently this is running directly of a switch that is PoE capable.

for what it's worth, I haven't had any disconnects since this AM when I switched the modem from QMI to MBIM mode.

[swwifty]

OK, so I think its a power issue.

I logged into GoldenOrb and noticed now that it was connected to B4 as primary and B5 like normal (while in MBIM mode). I mentioned earlier this AM it was connected to band 13 as primary and band 4 after switching from QMI to MBIM. After I switched it, I ran a speed test with no issues.

Just now, I ran a speed test again, now that it was back on the "normal" bands, and during the upload test the modem reset entirely. It has to be a power issue, just not sure right now what component is causing the issue...

Time to troubleshoot more

[swwifty]

Finally found the issue, that was quite the ordeal troubleshooting.

I started with swapping the USB cable between the PI and the USB enclosure for the modem. Same issue. I swapped the modem entirely with another MC7455 (luckily i have a spare) same issue. I tried swapping the PoE splitter, but ran into another issue with them not working (still not sure whats up with that.) I tried plugging in the modem to a different USB port on the PI, same issue. Lastly, I tried a Ubiquiti 802af PoE injector I had, and the issue went away. Huh. I plugged it back into the switch on the same port and rebooted the switch entirely. Same issue. I tried a different PoE port on the switch, and the problem is solved.

Moral of the story is try your PoE injector first like Jim suggested

I suspect that this port got damaged sometime in the past, but just now started manifesting the issue. I had an issue with the switch getting hit with static electricity from outside when my Ubiquiti nanostation didn't have shielded PoE cable attached to it. Hard lesson to learn, but there it is.

[JimHelms]

That is good news. I suspect there are a lot of random connection issues that could be resolved with replacing/updating the power supply.

[swwifty]

That is good news. I suspect there are a lot of random connection issues that could be resolved with replacing/updating the power supply.

Probably. It's so strange that it worked most of the time, except when the modem was trying to transmit at nearly full power. I also noticed it didn't happen when Band 13 was primary (probably cause it didn't need as much power for the cell to hear my modem) but only happened when Band 4 was primary.

[swwifty]

Wow what a roller coaster of troubleshooting this was.

I thought I had the issue resolved, and last night it started resetting on its own again.

I'll spare everyone the long troubleshooting story again, but turns out my PoE Splitter for the PI was also toast. The switch ports are acting funny (not giving full speed anymore) and the PoE Splitter smelt like burn electrical when I took it out.

I'm now using a Ubiquiti PoE injector and replaced the PoE splitter with a spare 100mbps version I had, and it seems the issues are good.

Time will tell for sure.....

[unbunchster]

Reducing your convoluted fun RPi prefers voltage at the top end of the spec

5.25 volts at whatever amps it wants. You can either use one of the inexpensive buck/boost converters on ebay/amazon or find the 5.25 volt usb power supply options on amazon. ~ $8 USD to $25 USD for these items.