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Cisco Employee

how to trace the source of TCN from core switch to interface of access switch?

how to trace the source of TCN from core switch (Catalyst 4500 L3 Switch Version 03.06.05.E, cisco WS-C4500X-32 (MPC8572) processor (revision 9)) to interface of access switch?

MST0
Spanning tree enabled protocol mstp
Root ID Priority 0
Address 0008.e3ff.fc50
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 0 (priority 0 sys-id-ext 0)
Address 0008.e3ff.fc50
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Te1/1/2 Desg FWD 2000 128.2 P2p
Te1/1/9 Desg FWD 40000 128.9 P2p
Te1/1/13 Desg FWD 2000 128.13 P2p
Te1/1/17 Desg FWD 20000 128.17 P2p
Te2/1/2 Desg FWD 2000 128.1282 P2p
Te2/1/13 Desg FWD 2000 128.1293 P2p
Te2/1/28 Desg FWD 5000 128.1308 P2p
Po11 Desg FWD 1000 128.2571 P2p Bound(PVST)
Po12 Desg FWD 1000 128.2572 P2p
Po13 Desg FWD 20000 128.2573 P2p Bound(PVST)
Po20 Desg FWD 1000 128.2580 P2p
Po110 Desg FWD 10000 128.2670 P2p
Po161 Desg FWD 40000 128.2721 P2p Pre-STD
Po162 Desg FWD 10000 128.2722 P2p Pre-STD
Po180 Desg FWD 40000 128.2740 P2p Pre-STD
Po181 Desg FWD 60000 128.2741 P2p Pre-STD
Po250 Desg FWD 5000 128.2810 P2p

 

 

Track the Source of a TCN
In itself, a topology change notification is not a bad thing, but as a good network administrator, it is better to know their origin in order to be sure that they are not related to a real problem. Identifying the bridge that issued the topology change is not an easy task. However, it is not technically complex.
Most bridges only count the number of TCNs they have issued or received. The Catalyst 4500/4000, 5500/5000, and 6500/6000 are able to show the port and the ID of the bridge that sent the last topology change they received. Starting from the root, it is then possible to go downstream to the initiator bridge. Refer to the show spantree statisticscommand for more information.
If you have the output of a show spantree statistics command from your Cisco device, use Cisco CLI Analyzer (registered customers only) to display potential issues and fixes. To use Cisco CLI Analyzer (registered customers only), you must login as a registered customer, and have JavaScript enabled.
 
There is no command show spantree statistics in Catalyst 4500
 
cdx01as38>en
Password:
cdx01as38#show spantree statistics
                   ^
% Invalid input detected at '^' marker.
 
cdx01as38#show spann
cdx01as38#show spanning-tree statis
cdx01as38#show spanning-tree statis
cdx01as38#show spanning-tree statistics
                              ^
% Invalid input detected at '^' marker.
 
cdx01as38#sh ver
Cisco IOS Software, IOS-XE Software, Catalyst 4500 L3 Switch  Software (cat4500e-UNIVERSALK9-M), Version 03.06.05.E RELEASE SOFTWARE (fc2)
Copyright (c) 1986-2016 by Cisco Systems, Inc.
Compiled Thu 02-Jun-16 04:02 by prod_rel_team
 
 
 
then i try show standby,  and use file analysis, it got error.
 
cid:b7ce178e-8991-4829-9c7f-90a1497cc62a
 
then i use show tech support to analysis in CLI analyzer
 
there is no loop or TCN keywords in result
is there another things related with TCN?
 
1 ACCEPTED SOLUTION

Accepted Solutions
Highlighted
Collaborator

Re: how to trace the source of TCN from core switch to interface of access switch?

hi, Try "show spanning-tree vlan x detail" It should show you number of topology changes,when last topology change and interface Thanks John
**Please rate posts you find helpful**

View solution in original post

4 REPLIES 4
Highlighted
Collaborator

Re: how to trace the source of TCN from core switch to interface of access switch?

hi, Try "show spanning-tree vlan x detail" It should show you number of topology changes,when last topology change and interface Thanks John
**Please rate posts you find helpful**

View solution in original post

Highlighted
Cisco Employee

Re: how to trace the source of TCN from core switch to interface of access switch?

i attached the result i searched.

but there are many 

 

i sorted the 5 largest changes

and 

i highlighted smallest last changes occurred time with yellow

i am not sure 00:00:00 mean nothing occur or the lastest

 

using latest change occur find

 Port 1308 (TenGigabitEthernet2/1/28) of MST1 is designated forwarding

which is a link to secondary site

 

but using BPDU sent or received number find port channel which connected to a juniper switch

 

which one is related with TCN ?

Highlighted
Cisco Employee

Re: how to trace the source of TCN from core switch to interface of access switch?

then i investigate number of BPDU sent

and find maximum sent is 570906520

and find maximum received is 403483675

 

as juniper vendor said TCN sent from cisco , cisco support said TCN sent from juniper

 

what does this sent mean?

do it mean "sent to this switch" or "sent to this port from this switch" ?

what does this received mean?

do it mean "received by this switch" or "received by this port"?

 

 

if using sent, find

 

Port 2571 (Port-channel11) of MST0 is designated forwarding
Port path cost 1000, Port priority 128, Port Identifier 128.2571.
Designated port id is 128.2571, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 3
Link type is point-to-point by default, Boundary PVST
BPDU: sent 570987196, received 403556083

 

 

if using received, find

 

Port 2571 (Port-channel11) of MST0 is designated forwarding
Port path cost 1000, Port priority 128, Port Identifier 128.2571.
Designated port id is 128.2571, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 3
Link type is point-to-point by default, Boundary PVST
BPDU: sent 571042972, received 403606345

 

 

cdx01as38#sh int po11
Port-channel11 is up, line protocol is up (connected)
Description: Po11 c3e05ms01 Ae70(xe-0/0/80,xe-1/0/80)

 

Highlighted
Cisco Employee

Re: how to trace the source of TCN from core switch to interface of access switch?

Am my finding correct?

 

is the TCN coming from 

cps01cr01-private# sh int Ethernet3/2

 

cps01as38#sh int TenGigabitEthernet1/1
TenGigabitEthernet1/1 is up, line protocol is up (connected)
Description: cps01cr01-pri-T3/1


cps01cr01-private# sh int Eth3/1
Ethernet3/1 is up
admin state is up, Dedicated Interface
Description: cps01as38 Te1/1

cps01as38#sh int Te1/1
TenGigabitEthernet1/1 is up, line protocol is up (connected)
Description: cps01cr01-pri-T3/1


cps01cr01-private# sh spanning-tree vlan 102 detail

MST0002 is executing the mstp compatible Spanning Tree protocol
Configured hello time 2, max age 20, forward delay 15
Root port is 385 (Ethernet3/1), cost of root path is 24000
Topology change flag set, detected flag not set
Number of topology changes 246446 last change occurred 0:00:15 ago
from Ethernet3/1
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Timers: hello 0, topology change 19, notification 0

Port 385 (Ethernet3/1) of MST0002 is root forwarding
Port path cost 20000, Port priority 128, Port Identifier 128.385
Designated port id is 64.4097, designated path cost 4000
Timers: message age 4, forward delay 0, hold 0
Number of transitions to forwarding state: 1
Link type is point-to-point by default, Internal
PVST Simulation is enabled by default
BPDU: sent 404, received 21228841

Port 386 (Ethernet3/2) of MST0002 is designated forwarding
Port path cost 2000, Port priority 128, Port Identifier 128.386
Designated port id is 128.386, designated path cost 24000
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 14
Link type is point-to-point by default, Internal
PVST Simulation is enabled by default
BPDU: sent 5954645, received 0

 

cps01cr01-private# sh int Ethernet3/2
Ethernet3/2 is up
admin state is up, Dedicated Interface

 

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