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

[Alex Carver]

Good point, the Uverse router does not have auto MDI/MDX capability on
its ports and not all switches have that either (or they have it only on
specific ports).  However, since this configuration worked at first and
now does not would imply the wiring was OK originally so crossovers
shouldn't have happened unless any of the building wiring was changed.

As for number of wires, yes 100Base-T only requires two pairs but the
other two dead pairs are actually very important for maintaining
impedance in the cable suitable for use at 100 MBit.

On 2019-04-11 12:11, Jim Kinney via Ale wrote:
> You might want to test the line in the wall and see if it's wired A/A,
> B/B or cross-over style A/B at the wall jacks. The color coding needs
> to be identical on both ends of the connection in nearly all cases.
> Unless the new switch is just too stupid. Used to be switch to switch
> REQUIRED a crossover cable. Most, but not all, are now smart enough to
> reverse in/out on plug-in. 
> On Thu, 2019-04-11 at 10:13 -0400, Derek Atkins via Ale wrote:
>> Hi,
>> Alex Carver via Ale <ale at ale.org> writes:
>>> It might still be a firmware update that at first didn't have
>>> VLANsupport and then later did.
>>> If you want to really test it, gather everything up together in
>>> onelocation and replicate the configuration you have (TV + Router
>>> intoswitch, switch into modem) with short patch cables.  If all
>>> works wellthen yes you've got a broken wire in the infrastructure
>>> wiring.  If itdoesn't work you've got a VLAN problem.
>>
>> When I connect the switch directly to the router locally, the
>> linklights up (i.e, I get blinky lights both on the router and on the
>> switch).
>> When I connect the switch through the wall, the link lights do
>> NOTilluminate, either on the switch or on the router.
>> A VLAN misconfiguration would not cause this behavior.
>>> It's also strange to see that your in-wall wiring is two pairs but
>>> wiredto 8p8c jacks?  Is it unshielded twisted pair (CAT3) or is it
>>> a bundledrun (straight wire) meant only for voice (in which case it
>>> should havebeen using 6p4c/RJ12 connectors).
>>
>> There are many many pairs of wires in there.  It's probably cat3
>> cable,but there are probably 5-6 pairs in there.  There is a single
>> cable withmany pairs that goes into the box in the other room, and
>> two pairs areconnected to the RJ45.
>> They need to use a 8p jack because it is ETHERNET.  Remember that
>> atleast 100BaseT only requires 2 pairs, and I think GigE also
>> onlyrequires 2 pairs.
>> I just don't understand why the switch is unhappy behind the 2 pairs
>> butmy other devices are just fine.  I.e., it doesn't matter whether I
>> plugin the Uverse box or the Smart TV -- both of them work
>> (individually) inthe other room.  But if I put the switch there, the
>> switch wont sync tothe router.
>> -derek
>>
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