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New Member

Catalyst-2950 port speed issues

Has anybody come across an issue with Catalyst-2950G Switches not being able to connect at 100MB when a 3Com 3C980 10/100 NIC is attached to one of the Fa0 ports ?

I can force the port to be 10MB HD as well as 10MB FD, but I cannot get it to run at 100MB FD (the card is a 10/100 NIC).



Re: Catalyst-2950 port speed issues


which IOS are you running?

Is the NIC configured also to 100MB FD, or left in auto mode?


and bug CSCdz32789 especially.



New Member

Re: Catalyst-2950 port speed issues

The swicth is running IOS ver 12.1(13)EA1 and (as far as I am aware) the NIC was set to 100MD FD.

I have found out that it is 3C980C-TXM 10/100 NIC. From what I have seen on the NIC documentation, there can be issues if one end of the link is set to Auto and the other set to 100MB FD.



Re: Catalyst-2950 port speed issues

Your cables may not be up to snuff. Being able to connect at 10, but not 100 is a hallmark diagnostic for a split pair on 3&6.

If your cable are not pinned-out to EIA/TIA 568A or 568B standards, they will not support full-speed connections.

Looking at the connector, clip down, with the end facing away from you, the colors should be (568B):

Orange-white, Orange, Green-White, Blue, Blue-White, Green, Brown-White, Brown.

The blue pair is inverted compared to the order of the other pairs.

For 568A, exchange the orange and green pair.

There is no technical advantage of 568A over 568B, but the "A" spec is compatible with US Telco color code usage.

Pair order DOES matter, if you just put the pairs side by side (like blue, green, brown, orange) then the conductor on pin 3 is from one pair, and the conductor on pin 6 is from another pair (a "split pair"): this completely eliminates the crosstalk canceling properties of the UTP design and seriously degrades the performance of the cable.

Just a shot in the dark, but it doesn't hurt to drag this out now and then.....

Good Luck