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Community Member

Cross Over cable

If i put a cross over cable between two interfaces on 2 Catalyst 3550 will speed will i get?

will it be 1000mb or less?


Re: Cross Over cable

depends on the cable cat 5 is 100Mbs

see this page

Community Member

Re: Cross Over cable

If the ports are set to "auto" detect speed, you will get a connection at the highest possible speed that the ports are capable of, regardless of the cable type. Whether the cable is Cat5 or 6 or 5e or 4 makes no difference


Re: Cross Over cable

I think what deilert is referring to is, the connection speed depends on whether the pinout of the crossover cable is for Fast Ethernet (two of four pairs) or for Gigabit Ethernet (all four pairs). Cat5 or better cable is specified for both Fast Ethernet and Gigabit Ethernet over copper.

If crossover cable is pinned out to cross the pairs for Fast Ethernet only, then Fast Ethernet is the speed that should come up on the 10/100/1000 autodetect. You should cross all four pairs to get it to come up as Gigabit Ethernet. Here's a link to the pinouts:

Of course, I am assuming you're talking about interconnecting two 3550 switches via 10/100/1000 ports. Obviously if you're talking about two 10/100 ports then the best speed you'll get is 100.

That being said, some switches out there have the ability to auto-cross ports, in which case the issue of Fast vs. Gig Ethernet crossover patches is no longer an issue. Just use a straight-through patch cable and be done with it. (Not sure if Cisco's switches do this, though. I guess I've got some research to do...)

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