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New Member

Network switching issue

Hi, All,

Network got shock on 14 Jul. as the attached log, any root cause ?


Network Infrastructure

1. Core switch 1 is connecting Core switch 2 through 4 G bandwidth port-channel

2. VLANs are definited in core switches and HSRPs are set up

3. Server switch is connecting only to Core switch 2

4. Floor switch loops with MST with two Core switches. ( root bridges are on core switches 1 and 2 )


Any help will be grateful.

Thanks a lot.


  • LAN Switching and Routing
New Member

Hi Ben Can you describe the

Hi Ben


Can you describe the problem more clearly. Do you mean the whole network was down. How do  you say this. Hope you have investigated the mac-flap notifications.



New Member

Hsrp link failure in the

Hsrp link failure in the network.

1. I want to what caused the network flapped 

2. HSRP link failure caused network flapping ?

3. Network flapping casued HSRP link failure ?

New Member

Hi  BenThis investigation

Hi  Ben

This investigation needs a light on the network connectivity more clearly. Probabaly at this point of time, we can say HSRP might not have created the issue, because HSRP is configured at VLAN level, so chances are less. Please check if the Neighbor down logs are observed first , if so check why there was a flap in neighbor status. Also as inayath suggested have you check if there was any hike in CPU. Check if there is any crash file created.


New Member

Hi,We are using core switch


We are using core switch with image = c6supp22-dsv-mz.121-8b.E18.bin.

No crash file found in the core switches.

Anything I should check further ?

New Member

 Did you take any sh-tech


Did you take any sh-tech output after the issue, that can help to understand the issue more clearly. At this point of time if not ospf related issue, and no changes in STP convergence time, we might not get the RCA.

Cisco Employee

Hi,Few things to look into


Few things to look into this:

1- Were there any high cpu reported on the box?

2- STP issue? As I see mac flap occuring could you please check on that?