Best Practice? on gigabit switches

[julian.young]

Dear All,

I am hearing a story the it is a cisco best practice to down grade ports to 100 FDX when connecting non  CISCO devices to a CISCO gigabit switch.  Apparently this is recommended because firmware compatibility can be guaranteed and not throttling the port can lead to significant packet loss and network problems.  The story is coupled with the comment that you can not explicitly set ports to 1000FDX, which is not the case on my switches, I can.

Does any one know the background to this?  Was this the case, is it still?  Is there a reference to a best practices paper about this?

regards

Julian

[hobbe]

Hi

AFAIK the only reason that I know of why it is not possible to set speed / duplex is that the standard only permits 1000/full duplex.

so there is no point in having settings since it can only be 1000/full.

Can you point me in the direction as to where the recomendation you are refering to would be ??

I have seen no such reference.

Good luck

HTH

[julian.young]

Sorry but it was word of mouth, I was trying to validate it. The source should be reliable but I fear out of date

Julian

Sent from Cisco Technical Support iPhone App

[Leo Laohoo]

I am hearing a story the it is a cisco best practice to down grade ports to 100 FDX when connecting non  CISCO devices to a CISCO gigabit switch.

I haven't heard of this for a long, looooooooooooooooooooooooooong time.

This "myth" is only valid for copper links (because you can't set the speed or duplex of a fibre optic port).  I heard about this when I was dealing with 3500, 2950, 2948-GE-TX and 2970 switches.  Nowadays with the new generation of switches it is almost a sin to hardcode speed/duplex setting when dealing with Cisco appliance connecting to another Cisco appliance.

The reason why this was rampant (particularly with the 2900/3500 and 2950/2955/2940) is because the "auto negotiation" function of the ASIC was, well, immature.  Put these models of switches and connecting them with modern clients and you'll see alot of duplex mismatch.