How to distinguish between jumper cable and network cable?

Ordinary network cables and jumpers are not the same thing. There is a difference. The Network Cable generally refers to the "4-pair twisted pair" without connectors, and the jumper refers to the network cable that has been terminated with an RJ45 head.

1. Of course, in addition to the RJ45 connector, the network cable can also be connected to the 110 connector, but this type of connector is not used much, so I won't say more about this.
2. If the customer wants to cross the wire, you are right to give him the jumper. But he emphasized that it was a cross line,
Then you supplied the wrong goods.
There are two explanations for the crossover you mentioned: one type of crossover is that the jumper must be done in a certain line sequence, like the 568A or 568B you mentioned.
When they connect the crystal head, they do not follow the line sequence of white orange, orange, white green, green, white blue, blue, white brown, and brown, but adjust the terminal sequence of several cores as needed, but no matter how you adjust it, The line sequence at both ends is the same.
Another type of cross-finger jumper has a 568A on both sides and a 568B wire sequence on the other. This kind of crossover is what the customer wants.
3. The jumper is not an ordinary network cable, but the jumper is a network cable with a connector. The 2 ends of the jumper are the same,
They are called parallel lines; there are differences, they are called cross lines. The difference between the two ends of the latter is what your customer requires.
4. Jumpers include but are not limited to crossover cables, which are just one type of jumpers. The 2 ends of the Crossover Cable are different.
Although what you took is the original 3m jumper from Anpu, generally, the jumper is parallel, that is, both ends are 568A or both ends are 568B.
Because what the customer wants is a crossover cable, that is, one end is 568A and the other is 568B.
So the customer was wrong.
Don't look for this kind of cross wire either. Generally this kind of thread is not in stock. All have to be ordered.