[ale] Why would a uverse ethernet work but not a switch?

Tue Apr 9 19:08:12 EDT 2019

Alan,

Thank you for playing, but you are completely overthinking the problem
(and not paying attention to what my problem is).

First, there is an AT&T router that provides me a local 192.168 network
and yes, it NATs, but that is irrelevant.

It has 4 RJ45 ports and Wifi.
One port is connected to the local Uverse TV box.
A second port is connected to my ATA phone.
A third port is open.
The fourth port is connected to the building wire, which is connected to
another room.  In that other room, if I connect my Uverse TV box directly,
it works.  And up until a week ago, if I connected my switch and then
connected the Uverse Box and my Smart TV to the switch, it all worked.

HOWEVER, as of now, the switch doesn't sync when connected.  This appears
to be a layer 2 issue, not a layer 3 issue.  My devices don't get an IP
address from my local router.

If I connect the Uverse Box directly to the wall (without the switch),
then the layer-2 syncs just fine.

I admit I have not tried connecting just the smart TV.

However, the switch will not sync to the router.  The link lights just
flash but don't stay on.

What I don't understand is why the uverse box will happily sync up on
layer 2 ethernet where my switch wont?

-derek

On Tue, April 9, 2019 5:22 pm, Alan Hightower via Ale wrote:
>
> I'm sure Uverse isn't providing multiple routable (real) IPv4 addresses.
>   So the router is likely NAT masquerading any downstream devices that
> try to initiate an outbound connection to the rest of the world.  In
> fact, it's very likely both your local router and an upstream network
> router are both NAT masquerading as there isn't any reason to have
> routable IPv4 addresses anywhere in AT&T customer infrastructure.
>
> So my guess is AT&T pushed a firmware update to the router to change the
> masquerade policy.  Why?  Because they are AT&T of course.
>
> If your SLA covers providing you with general Internet service via the
> wired router path, take it up with AT&T and have patience.  If they
> expect you to only get it via WiFi from the router, take it up with AT&T
> and prepare for failure.  Also if the later, you could turn a close
> proximity wifi client connection into bridge wired ethernet with a
> number of commodity devices.
>
> You can do some poking around and report back.  Plug a PC into the
> switch and see if you get a DHCP lease from the router.  Report back the
> lease details if any.  And if you do get a lease, make sure you can ping
> the default route and perform a traceroute to a North Star such as
> 8.8.8.8 and report back.
>
> -Alan
>
>
> On 2019-04-09 15:15, Derek Atkins via Ale wrote:
>> Hi,
>>
>> I'm temporarily living in an apartment while my house is being
>> renovated, and we have AT&T Uverse here.  Uverse uses ethernet for the
>> "remote" TV box, and until a week ago I had installed a switch to allow
>> me to plug in both the uverse box and my smart tv (the wifi there is
>> spotty).  See diagram:
>>
>> [router] - [wall] - [building wiring] - [wall] - [switch] - TV and
>> Uverse
>>
>> I was gone for a week and when I came back the switch was no longer
>> syncing to the router, so neither the TV nor Uverse were working.  At
>> first I thought it was the switch that went bad (there was a power
>> outage when I was gone), so I ordered a replacement.  However, the
>> replacement switch also does not work.  What is strange is that if I
>> plug the uverse box in directly to the wall it works fine.  Moreover,
>> if
>> I plug the switch directly into the router using a local patch cord it
>> works there.  So the only time the switch fails is when it uses the
>> building wiring.
>>
>> As I said before, I'm in an apartment so don't really have access to
>> the
>> building wiring.  I can ask the building management, but I suspect they
>> will foist me off to AT&T.  And if I go to AT&T, I suspect they will
>> say
>> they don't support switches -- and will ignore me because their Uverse
>> box works just fine.
>>
>> SO...  Any ideas where I go from here?  They are only using 4 wires (2
>> pairs) for the in-wall wiring, but that should be fine even for my
>> little netgear switch.  At least, it was until a week ago.  I don't
>> understand why the Uverse box works but a switch wont.
>>
>> Any ideas?
>>
>> -derek
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-- 
       Derek Atkins                 617-623-3745
       derek at ihtfp.com             www.ihtfp.com
       Computer and Internet Security Consultant