Port status up and down and up again

[owen2]

recently I have noticed my switches are showing log when I connect a new device to it.

The port is functioning well just odd to see these log.

LCP-SW1: Mar 01 09:01:09 GMT: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/1, changed state to up

LCP-SW1: Mar 01 09:01:21 GMT: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/1, changed state to down

LCP-SW1: Mar 01 09:01:28 GMT: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/1, changed state to up

the process is due STP or BPDU ?

[Leo Laohoo]

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@owen2 wrote:

when I connect a new device to it.

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IT is due to your NIC card.

[owen2]

Hi Leo,

the NIC card on my devices?

not the switches?

[Leo Laohoo]

NIC Card on your devices. That's how they behave.

Layer 1 goes down and then up.  (Line down/up)

Layer 2 goes down and then up.  (Protocol down/up)

The switch will reflect that behaviour and you'll see a link go down/up two times.  
Same behaviour when a PC wakes up from sleep.

[Georg Pauwen · Accepted solution]

Hello,

the NIC cards in your machines going to sleep because of inactivity. You could try and set the keepalive timer on your switchports to something higher than the highest interval seen in your logs, say 20 minutes. That woud mean that the switchport would not go down even after not getting a response from the connected device for 20 minutes, if that is what you want:

interface GigabitEthernet0/0

keepalive 1200

In addition, if you just want to get rid of the messages in your log, you can configure the logging discriminator below:

logging discriminator LINKSTATUS severity drops 3 facility drops LINK mnemonics drops UPDOWN

!

logging buffered discriminator LINKSTATUS 100000
logging console discriminator LINKSTATUS
logging monitor discriminator LINKSTATUS
logging host 192.168.100.10 discriminator LINKSTATUS

[omz]

Hi

A switch is in down state when there is nothing connected to the port or if its admin shutdown.

When a device is connected to a switchport .. %LINK-3-UPDOWN messages in the log show when the port status.

The messages are generated by the switch. Switchport status changes.. when a connected device goes sleep (e.g printer) or users shutdown their PC/laptops.