Consequently, our AT&T wireless service stinks when we are in the house.
Not that Verizon was any better - it wasn't. And it is neither company's
fault. In fact, I point out to people who complain about their wireless
the Verizon commercials where that guy is walking around saying "Can you
hear me now? Good!" - pay careful attention and you will notice
something - he is always outside! Never inside.
As soon as I caught wind of AT&T's indoor 3G microcell, I jumped on it.
In one sentence, think of it as a miniature cellular phone tower you put
in your house and it uses your wired high speed internet connection to
send your phone's voice / text / data over the internet instead of your
phone having to struggle to talk and listen to the cell tower that is so
many miles away. There are many other sites that describe the product in
way more detail, but that is a 20,000 foot view of the microcell.
Mine has been flakey since day #1 when I took it out of the box. When it
works, it works very well. But it tends to just go offline every 3-5
days. Flakey means "My cell phone won't see the microcell, rebooting the
phone doesn't fix it, the only thing that fixes it is power cycling the
After one too many reboots, I got frustrated with it and did some
on-line research. Found some posts on various forums that claimed I had
to re-load the firmware. Early versions had issues talking to the iPhone
5, which took a while for engineering to figure out and new firmware
fixed that. This device has no GUI whatsoever other than 5 LEDs that
light, blink, or change color. There is no user interface to the device,
which means the user is pretty blind - other than the LEDs.
Further research says the device will load up new firmware if you
completely remove it from your AT&T wireless account and re-add it.
So I did that. And it took forever to register - as in "Over 24 hours",
and at least two power cycles after I'd waited over 6 hours each time.
During one of those waits, I called AT&T tech support to see what they
could see, and at the time it hadn't phoned home in 4 or so days with a
GPS position so they very kindly agreed to send me a replacement even
though mine was out of warranty. At that moment, we both thought my 3G
microcell was dead.
But, minor miracle, somehow my blinking LED microcell magically
registered itself the next day. It still flaked out and went offline
after 4 days, but it wasn't completely dead.
A newly refurbished
So the new one arrives - unboxed, registered with AT&T online, put it
where the old one was, power it up - and wait. It gets GPS lock, sees
the local network, ... and then little 4 antenna bar icon on the unit
just keeps blinking and blinking and blinking, about 2 seconds between
blinks. I did some measurements and created this animated GIF - the new
non-registering microcell is on the left, my original microcell is on
the right and not powered, and my lovely 10 Mb/s hub I use for sniffing
data on the wire is sitting under them.
Note to self: Window blinds make a wonder analog brightness
adjustment, allowing perfect balance between the LEDs and the ambient
lighting necessary to see everything correctly! Normally the unit
wouldn't be upstairs, nor be connected via a network hub but a gigabit
Ethernet switch, nor sit on a radiator. But I wanted a decent portrait
showing the LEDs in case there is some hidden intelligence in there AT&T
or someone else finding this page finds useful.
So the unit does everything except find the AT&T wireless network to
phone into - at least that is what I thought seeing antenna bars
blinking. And in fact that is what AT&T tech support tried to tell me.
Another tech said that meant the microcell cannot see my network, that I
have a network problem.
But they are wrong. They are 100% wrong.
One meaning for this flashing light pattern is the microcell is
trying to phone home over the internet and the microcell is not seeing
any response from the system on the other side of the internet the
microcell is trying to talk to. There are many reasons this can happen,
including all those things tech support wanted me to try. But the
problem can also be because of an issue with AT&T, and the flat out
refusal to even consider that as a possibility until I've completely
disrupted my world is completely inexcusable. In fact, if the
servers the microcell is trying to talk to are powered off, the lights
will blink with the exact same pattern as if the microcell can't get out
of my location and onto the internet. The lights alone can't
tell the difference (I could make them tell the difference easily! Just
give me the source code and a couple of days... seriously...).
Tech support can't tell the difference, but I can - because I looked
at the data coming out of the microcell. Data on the wire doesn't lie.
is over, now for the juicy bits!
My first thought seeing blinking antennas was to move the unit to
another part of the house - maybe a tower was down and it couldn't shoot
RF signals in the direction I had it facing, so it moved upstairs and to
the other side of the house. No difference. I thought as a microcell it
might actually talk to another cell tower and not just my cell phone.
Still not sure if that is true or not - one of the tech support people
on the phone said they saw one of the indicators go green when I did yet
another power cycle, and the only way they could have seen that data was
over the air and not over the internet.
So last night fed up with a new unit arriving and not working, I
started digging in.
If you've read any of my other diagnostic articles, you know my first
tool of choice is often a network sniff. If I can see the packets and
who is talking to what, I can pretty quickly isolate a problem and know
what direction to go looking for a solution at. And this device is just
that - a networked bit of equipment that has to talk to other things to
So I took both units, hooked them into a network hub, hooked the
laptop up with Wireshark, and watched the data as both units powered up,
acquired an IP address, and attempted to talk to their home bases over
Knowing what I learned below, I contacted AT&T technical support,
spoke to the 3G microcell folks. They had me do all kinds of stuff that
were completely useless in fixing the problem - some of these activities
Power cycling (Been There, Done That, didn't fix it any of the last
Waiting yet another 90 minutes (BTDT),
Powering off my router (I refused, was sent higher up, she insisted, so
I lied and said I was doing that - I run a 24/7 operation and that was
an unreasonable hoop that would only disrupt my business and not fix
this problem at all.)
Disconnecting cables (a reasonable request. Probably 80% of network
issues are cable related. But I had all the data below already, and if
the cabling was a problem I wouldn't have that data. Asked - begged -
them to read the stuff below multiple times, none of the lower level
techs would look at it.)
One of the agents in the support chain whose name will not be
mentioned as I don't want to embarrass her insisted that all the lights
on the front of the microcell had to be on including the computer light,
and the fact it wasn't lit said I had a network or connection problem I
would have to fix before she could continue diagnosing the activation
Not true! AT&T Tech folks: You should really read your own support page, this is from
In all fairness, I understand and sympathize with tech support folks.
They probably have to deal with phone calls like "My brother in
California can't see my 3G Microcell here in Michigan, why isn't it
working?" all day, tirelessly and cheerfully explaining "Sir, the 3G
microcell only has a range of around 1000 feet and can't make it the
2000 or so miles across the United States. Thank you for choosing AT&T!"
I would gladly pay $2500 every year to be spread out among technical
support companies for this:
(if you like that, you need to spend a few hours at
http://xkcd.com and enjoy. This comic is
Ok, so now I'm going to get the propeller on top of my hat spinning
full speed. Hang on!
A sniff of
what the new brain-dead replacement microcell is doing
This is the just received AT&T replacement 3G microcell trying to
talk back to AT&T via the Internet. Network sniff was taken 4/1/2013
All screen shots are thumbnails and can be made larger by clicking on
them. First I'll show you the replacement failing microcell, then my
original microcell that still works. I have eliminated most of the
unimportant packets from this screen capture.
Interpretation for those not quite as intimate with network packets
as I am:
#2505 & 2512: The microcell is getting the time via Network Time
Protocol from the device at 188.8.131.52. It can talk fine and hear
back the time fine - this means the device can talk to the
internet just fine. This means no amount of resetting or power cycling
my local router, firewall, or any other equipment will fix the problem.
#2783: The microcell wants to phone home to AT&T, so it does a DNS
query to find where home is and looks for the address at
#2785: DNS answers that dpese.wireless.att.com
resolves to 184.108.40.206 or 220.127.116.11
#3701-3965: Repeated attempts to talk to 18.104.22.168, no response.
#4216-4487: Repeated attempts to talk to 22.214.171.124, no response.
Independent proof that 126.96.36.199 and 188.8.131.52 are both
completely offline as far as the 3G microcell is concerned:
(The microcell tries to establish a TCP socket on port 443 back to the
server. My Telnet command is trying to do the same thing. If the server was alive, reachable, and answering the screen
would have cleared to a black screen as telnet sees the connection is
established. Not that I can continue with the TLS handshake, but I can
at least see if the server is responding at all or not.)
Here is the consumer status screen showing that it hasn't phoned
home. This is from this morning, 4/2/2013, no change from anytime
Since the microcell is trying to talk to an AT&T server that does not
currently answer, the AT&T network is blind as to the status of this
microcell. The only way AT&T can talk to the device is over the radio
airwaves, at least until AT&T fixes the server this microcell is trying
to talk to. The microcell is calling over the internet to a pair of
servers that are not responding.
That is the problem - not my internet connection, not my router, not
my firewall, not my power supply, not the air in the house, not my
Ethernet cable, not the lights on the 3G microcell, not the position in
the window, the phase of the moon, or the sun shining on the microcell
This new microcell is trying to talk to
dpese.wireless.att.com resolves to 184.108.40.206 or
It can talk Network Time Protocol to 220.127.116.11
Look at the two addresses in top of each other:
18.104.22.168 - dpese.wireless.att.com
22.214.171.124 - One of the network time protocol servers at AT&T
If the microcell can't talk to the first but can talk to the second,
those two IP addresses are close enough they are likely in the same
Does it make sense if my microcell cannot talk to the first device
but can talk to the second device that the problem is anywhere in my
Think about that.
A sniff of
what the old microcell is doing - this one will register.
So here is the old microcell, that will register just fine. It is
using the same ethernet cable, same power supply, same internet feed,
same position in the window, same wooden window frame it is physically
sitting on, and breathing the same air as the other microcell. I'll walk
you through exactly how it is supposed to work...
A similar pattern to what is seen in the first sniff, except this one
works. So why do I want a new one? Because it flakes out and goes
offline every 3-4 days, requiring a hard power cycle and occasionally
requiring removal and re-registration. It is flakey. Has been since day
#1. Yes, I said that in the background already - but I wrote this part
before deciding this made a great "How to debug complex things nobody
else can figure out" article and needed background material above.
Anyway, here is what this box is doing.
#589-590: microcell is talking to 126.96.36.199 to do the NTP time
#595: This box is clearly different - probably running different
firmware. It wants to talk to dpece-hazelwood.wireless.att.com
- note this is not the same DNS name as the new microcell wants to talk
#596: DNS answers back that dpece-hazelwood.wireless.att.com
is at a 188.8.131.52 and 184.108.40.206 - note these are different
addresses than the replacement microcell resolves to.
#604-623, and onward: This is the proper TCP handshake - SYN packet
from the microcell, SYN-ACK from the server at 220.127.116.11, and an ACK
from the microcell back to 18.104.22.168.
This is working because 22.214.171.124 is alive and talking.
This is an AT&T server or AT&T DNS record issue. Either BOTH the
servers at dpese.wireless.att.com which resolve to
126.96.36.199 and 188.8.131.52 are not online and running the services
that respond to microcell communications via SSL on port 443, or the
addresses pointed to by the AT&T DNS Servers that resolve the addresses
of the name dpese.wireless.att.com are pointing to the wrong addresses.
Fix it already. Stop making me jump through your diagnostic hoops
that will accomplish absolutely nothing.
Days later, I got a call from someone asking my status - I asked
"Have you read the posted data?" - which they then did. He did some
research, said I was in 3 different support paths, and there wasn't much
more he could do that those support folks were already on it. So when he
asked if there is anything else he could do, I asked "Do you have the
ability to setup to swap out this unit for yet another one? Hopefully
one that is configured to talk to a server that is alive instead of one
that is dead?"
And short story, a couple of days later I had another microcell ...
and this one registers just fine!
And so far this unit has gone months without losing connectivity ...
I'm calling this problem solved!
If you found this helpful or not, please send me a brief email -- one
line will more than do. If I saved you a bunch of time (and thus $$),
and you wanted to show appreciation, sending a little love via PayPal or
an Amazon gift card is also very much appreciated!
I can be reached at:
das (at-sign) dascomputerconsultants (dot) com
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