Wednesday, January 27, 2010

Auto Negotiation Myth

The debate on auto negotiation is still on. I have faced the lot of outages because of auto negotiation. Sometimes you find that the working link with auto negotiation configured come up with half duplex consequences packet drops which may lead to the various outages. According to the IEEE 802.3u clause number 28, 802.3z clause number 37 standards the auto negotiation should be enabled on devices. This is optional but always recommended. The best is to read the SUN’s Ethernet Auto Negotiation Best Practises.
But I used to prefer to disable the auto negotiation and forcefully set the all capabilities. But after reading this paper, I come to know that after disabling auto negotiation we are not able to detect the following problems:-
1. Bad Cable Problem
2. Link failures
3. Link Partner Capabilities
4. Performance Issues
5. Pause Frames or Flow Control
If we are facing problems by enabling auto negotiation, In that case we need to talk to the vendors rather than disabling it.

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Aaron said...

Back in the day, we had nasty problems with autonegotiation. It actually came down to the fact that Cisco and IBB both threw their junk on the table and insisted that it was their way or the highway - you plugged in an IBM server to a Cisco switch and you always wound up with 100/half on the switch and 70% packet loss. With that experience, I started preaching of hard-coding everything and had no problems since. Now that everything's GigE, though, all the port and NICs are auto, and we've had no problems at all.

There's still something to say about setting a value to what you want instead of letting some mechanism set it for you.

shivlu jain said...

I had seen the same issues. But I am not able to understand if the IEEE is offering the standards then why the vendors are not maintaining it.

rahul said...

well in this post ithink something is missing,i will rate this post 4*