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New Member

auto-negotiation on switch ports

What are some pro's and con's of setting up switch ports with auto-negotiation versus maanually setting speed/duplex?

Cisco Employee

Re: auto-negotiation on switch ports

Autonegotiation allow two devices to agree upon the same language that they can speak.Both the set them to a least negotiated value.Most of the devices today have auto-negotiation built in and wrks great. As per the law of auto-negotiation both sides ahould be set to AUTO. In case if its not set then you will get into speed/duplex mismatch, CRC, Late collisions on the interface which will eventually slow down the process.

Manually setting the speed/duplex is kindda forcing the ports to work at the same speed to matter what is the condition.If you have manually set it and the devices connected to it doesnot support the same speed and duplex you will get into a lots of interface errors problem. Moreover if you have a very big network say 10K of users, hardcoding the speed and duplex on every switch port and PC is very tedious job. You have to spend a lots sleepsless nights to complete the activity and then trooublehsooting the problems in the middle of it.


-amit singh

New Member

Re: auto-negotiation on switch ports

Thanks. But are there failure stat's on both auto and manually setting speed/duplex. We are trying to come to a standard of port config. for speed/duplex.

Re: auto-negotiation on switch ports

I recommend you hardcode the following ports;




Leave the following in auto-negotiate


Hardcode the connection of important devices where more user use or rely on (i.e. fireall, router, server, etc..) since their connections are permanent. Leave to auto-negotiate the user connections because they move frequently. One of the good outcome for hardcoding is determining if one or more of the following is faulty; cabling, nic, and ports.

There is a higher failure if you leave important devices to auto-negotiate. There is also a high failure if you hardcode user ports, because user move frequently.

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