BCM5461 phy issue in 10M/Full duplex

BCM5461 phy issue in 10M/Full duplex

[Kumar Gala]

I was wondering if anyone has had any issues when trying to force a  
BCM5461 phy into 10M/full duplex.  I seem to be having an issue in  
the two managed switches I've tried this on but autoneg to 10/half.   
This causes a problem in that I start seeing a large number of frame  
errors.

I believe, but need to double check, that if I leave the BCM5461 in  
autoneg, and foce the switch to 10M/full that the BCM5461 will  
autoneg at 10M/half duplex.

Just wondering if anyone else has seen similar behavior with this PHY.

thanks

- kumar

Re: BCM5461 phy issue in 10M/Full duplex

[Rick Jones]

Kumar Gala wrote:
> I was wondering if anyone has had any issues when trying to force a  
> BCM5461 phy into 10M/full duplex.  I seem to be having an issue in  the 
> two managed switches I've tried this on but autoneg to 10/half.   This 
> causes a problem in that I start seeing a large number of frame  errors.
> 
> I believe, but need to double check, that if I leave the BCM5461 in  
> autoneg, and foce the switch to 10M/full that the BCM5461 will  autoneg 
> at 10M/half duplex.

Indeed, if one side is hardcoded, autoneg will "fail" and the side trying to 
autoneg is required by the specs (not that I know chapter and verse to quote 
from the IEE stuff :( to go into half-duplex.

Was 10M/Fullduplex ever standardized?  If not I could see where kit might not be 
willing/able to autoneg to that.

> Just wondering if anyone else has seen similar behavior with this PHY.
> 
> thanks
> 
> - kumar
> -
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Re: BCM5461 phy issue in 10M/Full duplex

[Maciej W. Rozycki]

On Wed, 18 Oct 2006, Rick Jones wrote:

> > I believe, but need to double check, that if I leave the BCM5461 in
> > autoneg, and foce the switch to 10M/full that the BCM5461 will  autoneg at
> > 10M/half duplex.
> 
> Indeed, if one side is hardcoded, autoneg will "fail" and the side trying to
> autoneg is required by the specs (not that I know chapter and verse to quote
> from the IEE stuff :( to go into half-duplex.

 Rather than forcing a PHY into 10Mbps, you may limit its advertised list 
of speeds/duplex settings and let autonegotiation do the rest.  It depends 
on how smart code to manage your switch is; it's certainly doable with 
Linux (you can do it with `mii-tool'; not sure about `ethtool') as long as 
the NIC driver supports the necessary ioctls.

> Was 10M/Fullduplex ever standardized?  If not I could see where kit might not
> be willing/able to autoneg to that.

 It is standard.

  Maciej