Problems connectivity GE on Foundry BigIron to Cisco 2950T

Mon Jan 16 00:22:26 UTC 2006

On Jan 15, 2006, at 6:02 PM, Sam Stickland wrote:

>
> Replying to my own email..
>
> I've found some sites that suggest it's not possible to disable  
> auto-negotiation on 1000Base-T since other operational parameters  
> are negotiated including selection of the master clock signal. I  
> was aware that flow control was negotiated, but not the clock signal.
>
> Can anyone elaborate?
>
> Sam
>

802.3ab claims that you can't disable autonegotiation on 1000Base-T,  
but lots of vendors allow you to anyway.

In 100 and 10Base-T, autonegotiation decides speed, phy type and  
duplex. In 1000Base-T, you add in a master/slave clock source  
negotiation. If autonegotiation is working, the master/slave thing  
just 'works'. If autonegotiation is disabled and your gear allows you  
to force 1000mbps, you also need to manually set which is the master  
and which is the slave. If you do nothing, most PC/server NICs force  
themselves into "slave" mode, and most switches force themselves into  
"master" mode. For the most part, this is correct and will result in  
it working fine. If it isn't, you have to hope your gear supports  
being able to toggle it. For example, in the BSD drivers for some  
Broadcomm and SysKonnect cards, setting the "link0" flag on the  
device will flip it. For Intel chips, there's a define in the driver  
source.

Personally, I'd look at the copper GBIC first. Many vendors have had  
trouble with supporting them, and have been the cause for problems  
for me in the past. Make sure the version of the OS on your device  
claims to actually support copper GBICs.