Our area has never gotten good cell phone coverage. Doesn’t really mater what carrier we used … AT&T or Verizon.
When AT&T announced that it was going to be making “MicroCells” available, I decided to get one … as it would help our cell phone coverage.
The MicroCell has been working fine for more than a year … but, all of a sudden (or so it seemed), it stopped working correctly.
I contacted AT&T and they tried a few things and asked me to try cycling power (unplugging it and plugging it back in). Nothing worked. I asked them to check to see if it was still under warranty … it wasn’t.
After I determined that AT&T wasn’t going to be able to help … I started thinking a bit more … and I remembered one of my favorite catch phrases: “If nothing’s changed, and something doesn’t work the same, then something’s changed”.
This got me to thinking … what did I change on the network recently that might have caused a problem?
Only one thing came to mind … I upgraded the firmware on my Netgear WNDR3700 router.
That reminded me of a setting I had to change on the router in order to get the MicroCell to work in the first place … I had to change the MTU value to a specific value … 1492. The details on the change, and how do to it on various routers, can be found on this AT&T knowledge base article.
I hadn’t thought about the MTU setting because, when I upgraded the firmware on the router, all the other settings had been preserved. This one, however, had been set back to it’s default (1500 I think).
After I changed the MTU value, and rebooted the router, the MicroCell worked fine.
I’ve seen MTU settings causing problems more and more lately, on both hardware and software. Good reminder to check that early in troubleshooting.