Interface shows up

Answered Question
Aug 20th, 2010
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Hi


I would  like to ask a question what could be the reason and how to fix it


I have a switch 3560 and on one of the ports a PC is connected, the PC is shutdown but the interface light is on and its also shows up.

why its doing it any help would be appreciated


Thanks

Asif

Correct Answer by Nagaraja Thanthry about 6 years 11 months ago

Hello,


Typically, most of the modern day PC's keep their NIC cards active even when

the device is down (hibernate). As long as the loop is complete, the switch

shows that the interface is up. Can you remove the Ethernet cable from the

PC and see if the interface still stays up? You can also check the interface

status by issuing "show interface " command.


Regards,


NT

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Correct Answer
Nagaraja Thanthry Fri, 08/20/2010 - 10:40
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  • Cisco Employee,

Hello,


Typically, most of the modern day PC's keep their NIC cards active even when

the device is down (hibernate). As long as the loop is complete, the switch

shows that the interface is up. Can you remove the Ethernet cable from the

PC and see if the interface still stays up? You can also check the interface

status by issuing "show interface " command.


Regards,


NT

Leo Laohoo Fri, 08/20/2010 - 18:47
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Like what NT said, it's because the NIC.  Even if the client is turned off but is plugged to a power source, the NIC will be "active" and listening out for special packets, such as Wake On LAN packets. 


You can demonstrate it yourself, find a PC which as been "turned off" by the OS and plugged to an active power source and the NIC light is on, however, if you un-plug this and you'll see the NIC card go dark.


In some cases, you know that the PC is turned off because some NIC go into "hibernation" by negotiating to 10 Mbps, Half-Duplex.


Hope this answers your question.  Please don't forget to rate useful posts.  Thanks.

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