auto-sense MDI/MDI-X and auto-negotiating questions
Posted on 2007-11-19
I had a couple of questions, so after a half an hour of google inestigating, I have come to some conclusions so I need to confirm/deny my thoughts. Here they are (correct me if I am mistaken):
1) MDI & MDI-X - to my knowledge those are are types of ethernet ports - MDI-X is crossed MDI. Ex: if I have one device with MDI port and one device with MDI-X port, then I need a straight cable. If both are MDI, then I need a crossover cable. If both are MDI-X, I guess crossover cable?
2) If the above is correct, then does it mean that connection between any two network devices (NIC, hub, switch, router, etc) needs crossed lines (1 -> 3 & 2 -> 6)
3) NIC's have MDI interface, while routers, switches and hubs have MDI-x interface. Is this always true, are there exceptions, and if there are, how would I know if port is MDI or MDI-X?
4) Newer switches/routers have autosense ports, which means that you can put any type of cable (crossover or straight), and it will detect and cross lines it if necessary. Are there any speed penalties while sending packets if I use straight cable between 2 routers - I guess no.
5) auto-negotiating - it means that it detects speed of connected network devices and automatically sets transmision speed of both devices to same speed (lower one). what is the benefit of this? What will happen if device doesn't have auto-negotiating feature?