TCN received from stackport1 on 3750

I was troubleshooting a network issue and during this time, I have done the following command on a 3750 stack:

show spanning-tree vlan 200 detail

Bridge Identifier has priority 20480, sysid 200, address a8b1.d36f.c670

  Configured hello time 2, max age 20, forward delay 15

  Current root has priority 8392, address 0021.e809.0670

  Root port is 568 (Port-channel11), cost of root path is 3

  Topology change flag not set, detected flag not set

  Number of topology changes 27 last change occurred 1w2d ago

          from StackPort1

As you can see, the source of the TCN is the StackPort1 on the switch!!!

But what is the meaning of this StackPort1 and how to determinate the real source of the topology change ?

In fact as my SSH session is open on the master and the TCN come from another switch of the stack, the source for my session is the stack port of the master switch. In order to determine which interface is really the source I have to open a session on each switch in order to find the TCN source.

For example, I have opened a session on the 2nd switch of the stack:

C3750#session 2

C3750-2# show spanning-tree detail | i from|exec|occur

 VLAN0001 is executing the ieee compatible Spanning Tree protocol

  Number of topology changes 26 last change occurred 1w2d ago

          from GigabitEthernet2/0/52

 VLAN0040 is executing the ieee compatible Spanning Tree protocol

  Number of topology changes 26 last change occurred 1w2d ago

          from GigabitEthernet2/0/52

As you can see above, we have found the real source of the TCN.

Install Netflow collector on Cacti

This tuto explains how to install the flowview plugin on Cacti. I have worked with Cacti 0.8.8b installed on an Ubuntu server.

Install and configure flow-capture

In order to capture netflow traffic, I have used flow-capture. In order to install it on Ubuntu, you can use apt:
apt-get install flow-capture

Once flow-capture is installed, you can configure the flow-capture.conf file:
vim /etc/flow-tools/flow-capture.conf

# Example 1:
# Capture flows from router at 10.1.1.10, listening at port 3000.
# Store flows in /var/netflow/flows/myrouter.
-w /var/netflow/flows/myrouter 0/10.1.1.10/3000

Add the file in dedicated folder:
mkdir /var/netflow/flows/myrouter

Configure a Router in order to export netflow

This configuration is different for each constructor. For example, I have configured an netflow export on a Cisco 4500:

flow record R1
 match ipv4 protocol
 match ipv4 source address
 match ipv4 destination address
 match transport source-port
 match transport destination-port
 collect counter bytes
!
flow exporter CACTI
 destination 10.10.10.10
 export-protocol netflow-v5 => flow-capture is only v5 capable
!
flow monitor M1
 exporter CACTI
 cache entries 1000
 record R1
!
interface Port-channel1
 ip flow monitor M1 input

Install and configure flowview on Cacti

Download the flowview plugin (http://docs.cacti.net/plugin:flowview) and untar it in:
/usr/share/cacti/site/plugins

Go to the Cacti console
Configuration>Plugin Management
And enable Flowview

Configure the path in order to read the netflow file created by flow-capture:
Go to the Cacti console
Configuration>Settings>Misc
Under Flows directory, specified your folder (for example /var/netflow/flows/)

Not able to execute 'copy running-config startup-config' command

Today, I have encountered the following problem:

MY-SWITCH#copy running-config startup-config
startup-config file open failed (Device or resource busy)

In a first step, I was thinking that the nvram: was corrupted because I was not able to see files in the nvram (dir nvram:). In fact, we were 2 users connected on the switch.


MY-SWITCH#show users
    Line       User       Host(s)              Idle       Location
*  1 vty 0     admin      idle                 00:00:00 10.10.10.10 => My session
   2 vty 1     admin      idle                 00:07:09 10.10.20.10

 Also, I have just ejected my colleague with the following command:

MY-SWITCH#clear line 2

After that, I was able to backup my configuration.