auto-sense MDI/MDI-X and auto-negotiating questions
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?
Thanks, Goran
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?
Thanks, Goran
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ASKER
Tnaks guys for the answers. I am a little confused now by this statement:
>> Switches and Hubs are usually MDI-x but routers are normally MDI
Does this mean (assuming that if switch & router don't have auto sense feature)
nic (mdi) to switch (mdi-x) needs straighthrough cable
nic (mdi) to router (mdi) needs crossover cable (like nic (mdi) to nic (mdi) does)
router (mdi) to switch (mdi-x) needs straighthrough cable
since in question two I say
>> 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)
Goran
>> Switches and Hubs are usually MDI-x but routers are normally MDI
Does this mean (assuming that if switch & router don't have auto sense feature)
nic (mdi) to switch (mdi-x) needs straighthrough cable
nic (mdi) to router (mdi) needs crossover cable (like nic (mdi) to nic (mdi) does)
router (mdi) to switch (mdi-x) needs straighthrough cable
since in question two I say
>> 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)
Goran
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ASKER
Well, I knew most of those (didn't know the one pc to printer), I just like to understand things and not to learn them as they are. :) One thing you didn't mention is switch to router and router to router - is it crossover too, and is there any general rule about what port number should I use when connecting switches and routers.
Goran
Goran
Router is considered the same as a PC, unless it has a built in switch like most SOHO routers, in that case, they can use either a straight or a crossover. Router to Router is crossover, same as a PC, with above exceptions.
ASKER
Ok I got it now, thanks guys for all the help.
Goran
Goran
The MDI-X is auto sensing on most of the new Cisco switches, but the preferred method on a switch if connecting two switches together is to disable MDI-x and use a crossover between them.