[CentOS] how to enable Flow Control on CentOS?

Les Mikesell lesmikesell at gmail.com
Fri Jul 8 23:06:06 UTC 2011

On 7/8/2011 5:50 PM, Giles Coochey wrote:
> On 07/07/2011 17:30, Les Mikesell wrote:
>> Old Cisco switches - and Cisco's advice about how to work around their
>> problems - are just the main reason that anyone would ever have turned
>> off auto-negotiate. And it is a big problem if you only turn if off at
>> one end which is what you end up with as you start to change
>> equipment, because the other end will always get it wrong. These days,
>> if a device doesn't negotiate properly you should probably just
>> replace it.
> The problem is not the auto-negotiation iteself, but the fact that if
> one side hard codes its speed to 100-Full Duplex then the other side
> cannot auto-negotiate to 100-Full Duplex. It also needs to be hard-coded
> to 100-Full duplex - The auto-negotiation is not a "I'll do what you're
> set to" type protocol, but a "let's see what's best for us" protocol.
> There was actually never any problem with auto-negotiation itself - it
> did exactly what it said on the box, just that it didn't work if either
> end turned it off and hard coded it's speed.

Yes, if it hurts, don't do it.

> Having seen my fair share of performance problems, if you don't have
> console access to both interfaces then agree on the speed and duplex and
> hard code it - saves a lot of faffing about and almost always works a
> treat.

Turning off negotiation pretty much guarantees problems if anything 
changes at the other end or you use an unmanaged switch.  And the 
gigabit spec requires auto-negotiation.

   Les Mikesell
    lesmikesell at gmail.com

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