UP/DOWN Status

Unanswered Question
Nov 16th, 2007

What are the usual issues when an interface (ethernet) is in an UP/DOWN status . DOWN = Protocol. Would it show this status if nothing was plugged in to the ethernet port..


I have this problem too.
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danny9797 Fri, 11/16/2007 - 07:23

Thats what i thought, nothing physically connected or a problem with the connected device...thanks

Pavel Bykov Fri, 11/16/2007 - 09:07

PROTOCOL DOWN state means Second OSI layer is not up.

If it's an SVI on interface (L3 interface) and no devices are connected, it will be down, because VLAN is down (no devices are connected)

But it's because there is a problem with Second Layer - it's turned off (because there are no devices - so it's not a BAD problem, but that's why it's down).

So devices can be connected, but one is talking different Ethernet protocol version than the other, or they are connected over different protocols (like serial line and one is using HDLC and the other PPP), or stuff like that... but basically you have to think - what is there on second layer, and why is it DOWN.

Hope this helps.


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