Spee and duplex configuration

Unanswered Question
Jul 15th, 2009

I need any recomendation interconnecting lan switches to server, what is the recomendation about the speed and duplex?, is better force this parameters or auto mode?

I have this problem too.
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Leo Laohoo Mon, 07/20/2009 - 14:51

Rule of thumb I am using.

Force duplex and speed (both sides) settings when switch is a 10/100/100Base (aka Triple speed) but server is a DUAL speed. This is also true when your server is triple speed and the switch is only dual.

Autonegotiate when switch and server is Triple speed.

Hope this helps.

Danilo Dy Mon, 07/20/2009 - 20:01

For devices that have static IP Address and in fixed location (specially critical devices like routers, firewall, servers, etc), I hardcode the speed/duplex. Except for those devices that don't support hardcoding the speed/duplex (e.g. GE interface of non-Cisco devices like PacketShaper, HP Unix).

From what I understand in the past, there is no standard for auto-negotiation thats why every vendor set their own standards for auto-negotiation. Do take note that this is in the past.

I have experienced that devices from same vendor configured in auto-negotiation even using good quality cable experiences speed/duplex mismatch overtime or during maintenance (IOS/OS upgrade, System Reboot). You will be surprised that I experienced that between a Cisco Catalyst Switch and Router after two years in production and nobody touch them, suddenly they have a duplex mismatch :).


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