straight or cross-over

Unanswered Question
Jul 22nd, 2008

Does the switch port/ router port has to be in auto mode before it can automatically determine whether the cable has to be a straight or cross-over? I guess if the interface has this capability we only need straight cable? IS there any limitation in terms of speed , media type etc?

I have this problem too.
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javickas1 Tue, 07/22/2008 - 07:42

I believe the auto to which you refer is the speed and duplex autonegotiation setting.

I'm pretty sure that if the switch can autodetect straight thru vs crossover (some can, some can't) then it will do that without any intervention on the users part. Just plug it in and it works.

garytayl Tue, 07/22/2008 - 07:42

When you enable Auto-MDIX, you must also set the speed and duplex on the interface to auto in order for the feature to operate correctly.

michaelchoo Tue, 07/22/2008 - 15:13

As far as routers go, from memory, I've only seen 800 series that allow you to switch between straight through or cross-over (using a button - maybe new ones are auto-mdix).

With switches, anything from 2960, I think, supports auto-mdix, which should be enabled by default, hence you shouldn't have to do anything. Some older Ethernet modules for 4500 or 6500 may not support auto-mdix.

Personally, I'd still prefer to use cross-over when you think you need it, although the switch may support auto-mdix. Reason being, cross-overs are traditionally used for inter-switch links over copper. Hence, it's better to use cross-over with different color to make it stands out (usually red, sometimes pink).


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