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New Member

Need help for choosing auto/half/full duplex?

I'm starting a brand new network. Migration token ring to Ethernet. What would be the best scenario/choice to make in regards to duplex (on 2950 and the NIC). Can you post me some of your recommendations and http link that discuss about it. Thank you

4 REPLIES
Cisco Employee

Re: Need help for choosing auto/half/full duplex?

Auto-Auto is the way to go. It is a best practices. Only you manual if you need to and if you do. Make sure you do both sides of the link.

http://www.cisco.com/warp/public/473/103.html#subfirstthree

New Member

Re: Need help for choosing auto/half/full duplex?

Auto-Auto can lead to trouble. See this

http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a00800a7af0.shtml

I ALWAYS set speed/Duplex at each end, and I learnt that the hard way!

Bronze

Re: Need help for choosing auto/half/full duplex?

Some swear by auto-auto and others don't trust it. My preference is to use auto-auto for workstation/server ports and manual for trunks, Etherchannel, etc. Autonegotiation was pretty bad 5 or so years ago and hence got a bad reputation. But it's gotten a lot better, and even Cisco -- who used to advise against it -- now recommends using it.

The problem with doing it manually across the board is that you have to remember to do it on both ends, as workstations and servers default to auto. Setting one end to manual and one to auto results in a duplex mismatch, which destroys performance.

New Member

Re: Need help for choosing auto/half/full duplex?

In my experience the fixation of speed and duplex settings is fully dependable on the type of usage of the port, witch means for permanent connections like servers , routers uplinks and that kind of usage it is always wise to force a fixed config on both sides, if the connection is a workstation or laptop, there should be nothing wrong with auto detect.

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