why i shouldn't always use full duplex

[rubingerser]

if the other side supports it ?or does it better to leave it on auto negotiation and let the server and the server deside (not including jumbo frames )?

and should i use  auto negotiation on switch (switch for server ) or should i configure manully important ports?

[Michel Hegeraat]

There are pro and cons. 

A connection that is fixed on both sides, so no negociation of any kind, is up faster than a negociated port.

If a port dies and all you need to use another port, you probably will have to configure the new port. If ports are in auto, and all on the same vlan, then you can just repatch.

I prefer the fixed scenario, but I've heard of scenarios with cisco connected to cisco where only auto-auto worked as expected.

Cheers,

Michel

[Christopher Bell]

This is a pretty common debate .  To me, it really boils down to management practices and how big your network staff is as well as their patience level with tedious troubleshooting tasks.  We found that trying to hard set devices just lead to troubleshooting network issues later when server admins or techs didn't remember to set matching duplex/speed settings.  You don't really loose anything you are going to miss as far as speed by setting everything to auto where you can.  You are going to inevitably find circumstances when you HAVE to hard set them, but it's my opinion that should always be avoided when possible. 

My vote is for auto neg.

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