Ports changing state randomly

[RFC_2549]

Hello,

I have a switch witch some port changing state randomly...like this:

Jul 24 14:58:59.374 CEST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/3, changed state to down
Jul 24 14:59:00.378 CEST: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/3, changed state to down
Jul 24 14:59:19.307 CEST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/3, changed state to up
Jul 24 14:59:21.070 CEST: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/3, changed state to up
Jul 24 14:59:32.979 CEST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/3, changed state to down
Jul 24 14:59:33.982 CEST: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/3, changed state to down

And some hosts flapping between different interfaces.

Switch is in rapid-pstv mode...

The issue started when we added a switch to the network but I think that the problem is not related to STP because if I type "sh spanning-tree summary" all vlans hve stp active and ports in forwarding.

What can I check?

Ports have bpdu guard and portfast enabled...

Thank You!

[Reza Sharifi]

Hi,

Is port 1/0/3 connected to the new switch?

Can you post the output of "sh run int g1/0/3"?

If this port is not connected to the new switch, can you also post the config for the port that is connected to the other switch?

HTH 

[RFC_2549]

no, the new switch is in another location...the ports that are changing state are located in an old switch :) between this switch and the new one there are other switches so they are not directly connected

later I will post the output of the g1/0/3

Thanks

[RFC_2549]

hello, here I report the config of the port...similar to the conf of the other ports that have the issue

interface GigabitEthernet1/0/3
switchport access vlan 303
switchport mode access
switchport nonegotiate
spanning-tree portfast
spanning-tree bpduguard enable

thanks

[paul driver]

Hello

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@RFC_2549 wrote:

The issue started when we added a switch to the network but I think that the problem is not related to STP because if I type "sh spanning-tree summary" all vlans hve stp active and ports in forwarding.

---

This could be exactly the problem -  do you have trunks on the switch and is it interconnected to other switches on multiple ports?
Is this switch part of any stack?

Whats the switches cpu utilization showing?
Have you checked the physical cabling?

[RFC_2549]

Hello!

This could be exactly the problem -  do you have trunks on the switch and is it interconnected to other switches on multiple ports? The switch have only one trunk to the core, the ports that are facing the issue are access ports for computers
Is this switch part of any stack? no

Whats the switches cpu utilization showing? 7% of utilization
Have you checked the physical cabling? no, and I can't do it, is a remote site and I cannot say to someone to check the cables :( 

The switch have a trunk port that arrives on the core...the new switch is situated in the opposite part of the network and has only  one trunk port trat arrives on another switch

Thank you!