Why is data being transmitted when the 6th core is damaged?

Question

Computer networks

The PC is connected to the Cisco Catalyst 2960 gigabit port, auto-negotiation is set on the PC and the cisco, the connection is at a speed of 1 Gb / s. When the green wire is torn, the port drops into 10 Mbps duplex. With pings, the loss is about 90%, the rest of the packets pass with a response of 0.3 ms. As far as I understand, if one of the 8 cores is damaged, it is no longer possible to raise the port to gigabit, respectively, it tries to 100 and 10, but the core that participates in data transfer according to these standards is broken. Why is there actually a connection, albeit with such losses?

Answer 1

And there is. For 10 and 100, two pairs are enough (O, BO, Z, BZ), and all four are used for gigabit. If one of the conductors of the main signal pair is broken, then the signal will go along the second one, but this signal will not have a mirror image copy, because of this it will receive large pickups and will be difficult to recover when recognizing hence the loss. All equipment, including network equipment, initially operates at the lowest possible speeds, for ethernet it is 10mb / s, only then, after establishing a connection, the devices, if possible, agree to switch to other modes and speeds.

Answer 2

accordingly, he tries to 100 and 10, but the vein that participates in data transfer according to these standards is broken.

One of the two transmission media is damaged. Because for 100 and 10 only 2 pairs are used.
Lived numbers: 1,2,3,6 or 4,5,7,8.
If two channels are damaged SIMULTANEOUSLY, data transmission will become impossible.

Answer 3

Parallel transmission, interference... Have you ever looked at how networks work?
If the 6th conductor is damaged, the network drops to the level of 10 Mbit half duplex.
In normal mode - one pair of reception, the second - transmission. Why and full duplex.
One pair is open - we go down to half-duplex - receiving and transmitting one pair in turn.
By the way, it is quite likely that if the connector is turned off and on when the conductor is open, the line will not rise at all;) Negotiation starts from 100 Mbps, but it is impossible. But already on an agreed connection, when capabilities are transferred - then it is possible to go down. But at the same time, if both devices are manually transferred to 10 Mbit half duplex, the connection will rise.