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

Tue Apr 9 20:26:35 EDT 2019

I believe that AT&T has been VLANing the TVoIP data.  An ordinary switch
that doesn't have VLAN capability may not be able to handle the mangled
802.1Q tagged packet so it will just dump it on the floor instead of
routing it onward.  This would be why the Uverse box direct to the wall
works but not through the switch.

You would have to sniff the packets to see what VLAN the TVoIP data is
on and what VLAN the normal connection to your router is on (this one is
most likely untagged) then replace your switch with a VLAN capable unit
and set up the ports accordingly.

I have an AT&T modem as well (though my ATA is in the modem rather than
external) and occasionally in the logs I do see messages about VLANs.
However, I don't get TV service over the wire, I have satellite so I
don't have a TV box to play with.  My parents also have AT&T but their
TV box is wireless and connects to a wireless adapter plugged into the
modem so that might be another way out.

On 2019-04-09 16:08, Derek Atkins via Ale wrote:
> 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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