What Happens When You Configure duplex:auto/speed:1000?

[Translator]

Can you tell us about the basic operation of Cisco equipment?
This is a question if you have configured the following settings in an Interface that connects two Switch.
SwitchA duplex:auto/speed:1000
SwitchB duplex:auto/speed:1000

What are the following conditions?
1. No Linkup
2. Linkup Normally with a Crossover Cable
3. Linkup Normally with a Straight Through Cable
4. Other

[joshqunismayilov]

Hello , 

You can read this topic https://www.cisco.com/en/US/docs/switches/lan/catalyst3850/software/release/3se/consolidated_guide/b_consolidated_3850_3se_cg_chapter_011101.html

1. No Linkup >> If one switch does not support Auto MDI-X and a straight-through cable is used instead of a crossover cable, the link might not come up.

2. Linkup Normally with a Crossover Cable >> If the switches do not support Auto MDI-X, a crossover cable is required for a successful link.

3. Linkup Normally with a Straight Through Cable >> If the switches support Auto MDI-X, they will automatically detect and adjust the TX/RX pairs, allowing a straight-through cable to work.

4. Other >> If both Switches are modern / Auto MDI-X should work.

A straight-through cable in modern Cisco switches with Auto MDI-X support should work, but if there’s no Auto MDI-X, a crossover cable is necessary.

Thanks !

[Translator]

@suzuki2502 

1. No Linkup >> If one switch does not support Auto MDI-X and a straight-through cable is used instead of a crossover cable, the link might not come up.

2. Linkup Normally with a Crossover Cable >> If the switches do not support Auto MDI-X, a crossover cable is required for a successful link.

3. Linkup Normally with a Straight Through Cable >> If the switches support Auto MDI-X, they will automatically detect and adjust the TX/RX pairs, allowing a straight-through cable to work.

4. Other >> If both Switches are modern / Auto MDI-X should work.

A straight-through cable in modern Cisco switches with Auto MDI-X support should work, but if there’s no Auto MDI-X, a crossover cable is necessary.

Thanks !

[Joseph W. Doherty]

A traditional Ethernet copper RJ45 jack is wired one of two ways, MDI or MDI-X.

For the link to work, tx/rx need to cross over between the two devices.  This can be done within the cable or ports, but not cable and ports.

I.e.

Straight cable and one jack MDI and other jack MDI-X.

or

Cross over cable and both jacks same.

Generally two like devices, such as interconnecting two switches will usually have same kind of jack, so cross over cable would normally be required.

With auto-MDI/X jacks, if either or both sides have it enabled, either cable type may be used.