From: James Ventre (messageboard@ventrefamily.com)
Date: Fri Nov 18 2005 - 15:05:03 GMT-3
Gigabit negotiatio avoids the negotiation problem 10/100 networks had of
hardcoding one side. If you hard code one side of a gig link - the
other side will stay down/down. Gig negotiation is a good thing - you
really shouldn't disable it since it also controls things like flow control!
Your case is a bit different - cause you're hardcoding both sides. What
is probably happening is that you're losing your MDIX auto functionality
(auto crossover cable) by hardcoding the line speed.
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat2970/12119ea1/2970scg/swint.htm#wp1193977
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.
Auto-MDIX is supported on all 10/100/1000 Mbps interfaces and on
10/100/1000 BASE-T/TX SFP interfaces. It is not supported on 1000
BASE-SX or -LX SFP interfaces.
James
Capt.Spock wrote:
> I have couple of 2970 switches connecting to a mix of other switches like
> 2970,6500,etc
> Some GIG connections are down if I set FULL 1000 on both the sides but come
> up when I do AUTO AUTO on both the sides. They come up with FULL and 1000!!!
> These are between 2970 (same breed)
> What makes the connection to go down when the DUPLEX and SPEED are set
> manually instead of AUTO??
> Any info is appreciated!
>
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