spanning tree flapping

[alon to]

Hello,

We have 2 devices connected in stp mst mode.

On regular time - 1 link is in block status (Backup link) - Te4/2

Sometimes we have problem with the primary link (Te3/1) and the STP protocol change status from forwarding to blocking (flapping)

how can i prevent the primary link (Te3/1) to flap more then 3 times (MAX) ?

because of the "flapping status" the backup link cannot work ok.

006497: 05:37:27.013 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te3/1 instance 0 moving from forwarding to blocking
006498: 05:37:27.013 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te4/2 instance 0 moving from blocking to forwarding
006499: 05:37:27.013 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te3/1 instance 1 moving from forwarding to blocking
006500: 05:37:27.013 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te4/2 instance 1 moving from blocking to forwarding
006501: 05:37:27.033 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te3/1 instance 2 moving from forwarding to blocking
006502: 05:37:31.457 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te4/2 instance 0 moving from forwarding to blocking
006503: 05:37:31.457 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te3/1 instance 0 moving from blocking to forwarding
006504: 05:37:31.457 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te4/2 instance 1 moving from forwarding to blocking
006505: 05:37:31.457 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te3/1 instance 1 moving from blocking to forwarding
006506: 05:37:31.457 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te4/2 instance 2 moving from forwarding to blocking
006507: 05:37:31.457 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te3/1 instance 2 moving from blocking to forwarding
006508: 05:37:46.457 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te4/2 instance 2 moving from blocking to learning
006509: 05:38:01.457 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te4/2 instance 2 moving from learning to forwarding
006510: 05:42:43.095 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te3/1 instance 0 moving from forwarding to blocking
006511: 05:42:43.095 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te4/2 instance 0 moving from blocking to forwarding
006512: 05:42:43.095 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te3/1 instance 1 moving from forwarding to blocking
006513: 05:42:43.095 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te4/2 instance 1 moving from blocking to forwarding
006514: 05:42:44.842 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te3/1 instance 2 moving from forwarding to blocking
006515: 05:42:46.845 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te4/2 instance 0 moving from forwarding to blocking
006516: 05:42:46.845 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te3/1 instance 0 moving from blocking to forwarding
006517: 05:42:46.845 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te4/2 instance 1 moving from forwarding to blocking
006518: 05:42:46.849 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te3/1 instance 1 moving from blocking to forwarding
006519: 05:42:46.849 ISR: %SPANTREE-SP-6-PORT_STATE: Port Te4/2 instance 2 moving from forwarding to blocking

thanks,

Alon.

[Mark Malone]

The only way I know i can think of to track issues like this at layer 2 is through EEM ,could try something like this below script and when the syslog is seen 3 times within 10 minutes it should shut the link that's causing an issue , you could alter the script to whatever times , just an option there maybe a  better way

event manager applet STPISSUE
 action 1.0 cli command "enable"
 action 1.5 syslog msg "ISR: %SPANTREE-SP-6-PORT_STATE: Port Te3/1 instance 0 moving from forwarding to blocking" occurs 3 period 600
 action 2.0 cli command "conf t"
 action 3.0 cli command "interface t4/2"
 action 4.0 cli command "shutdown"
 action 5.0 cli command "end"

[alon to]

Thanks for your response.

is "errdisable" - dtp-flap option will help in this case ?

Ten 3/2 + Ten 4/2 - is trunk interface.

Thanks,

Alon.

[paul driver]

Hello

If applicable depending io your need rely on stp or not. You can use a flex link with premption, this will negate STP and still will allow you to have a primary and backup link.

Reveiw it here

res
Paul