Within Cisco's best practices for the large L3 switches (http://www.cisco.com/en/US/products/hw/switches/ps700/products_white_paper09186a00801b49a4.shtml), they recommend for 100 Mbps "As a rule, first use autonegotiation for any type of link partner." but also recommend if there's a problem configure for 100/full. For gig, they have "Enable Gigabit negotiation on all switch-to-switch links and, generally, on all GE devices."

My experience has been with current gen equipment, there's often less issues with auto working correctly vs. someone forgeting to properly configure both sides of the connection expecially when for some reason they connect to a different port (like when dealing with a hardware failure).

I think you will see very few problems between cisco devices leaving them as auto . And unless you run into a specfic problem I wouldn't hardcode them . We run into very few problems for speed/duplex anymore and when it is it is usually because the "server guys decided to hardcode the speed /duplex because they fail to understand the implications of hardcoding . They think if they hardcode the server the switch will automatically adjust itself to 100/full and we all know that isn't true it will default to 100/half.

Another way to avoid the problem maybe is to configure (config-if)speed auto 10/100/1000

a middle way to force the speed with autoneg.

But for duplex settings not possible.

Thanks to everyone who responded.

I think the gerneral concensus is that auto between cisco devices is OK and works. And Auto between servers (and non-cisco devices) but use with caution.

In Edisons URL i picked up the follwoing statement.

"Because of these recent issues, the use of autonegotiation is regarded as a valid practice."

Cheers

Andy