03-16-2024 09:52 AM
Hi,
I have been testing MST in my lab which has 3x Cisco Catalyst WS-C2960CG-8TC-L switches.
I configured only MST and LACP on each switch and connected them in the ring topology. Test is to see how much time it takes for convergence in such conditions.
My expectations were it should take around 2 seconds, but results show its always somewhere around 5 seconds.
I have set all three timers (forward-time, hello-time, max-age) to minimum values and even set on the backboneFast feature, but it didn't make any effect.
Are there any configuration changes I need to make to reach expected 2 seconds convergence time?
Is it possible that these small factor devices are somehow hardware limited for STP performance?
Thanks
Petar
03-16-2024 10:06 AM - edited 03-16-2024 10:14 AM
If I am right you need fast rate LACP to make SW faster shut the Port channel when it fails.
MHM
03-16-2024 10:10 AM
how is your configuration looks like.
check the one of the good explanation from @peter
https://community.cisco.com/t5/switching/mstp-convergence-time/td-p/3380437
04-25-2024 07:40 AM
Thanks guys, after further testing we managed to get 2 second convergence time, seems like some config was missing.
When using LACP and we disconnect one port channel we get 2 seconds convergence, but after some time if we reconnect the same port channel convergence is 7.7 seconds. this is the only way we dont get the ecpected 2 seconds time.
04-25-2024 08:16 AM
I can not decided which part of config effect this delay
But share the config
Abd keep in mind divide mst to two half or more abd put all vlan to this instance, even if you dont use these vlan
MHM
04-26-2024 02:33 AM
Hello
@pit-maravich wrote:
My expectations were it should take around 2 seconds, but results show its always somewhere around 5 seconds.
May I ask what the timers you have manually set and what convergence conditions are you basing this on?
The standard mst bpdu expiry should be 3x the hello which is 2 seconds so if you are getting 5 seconds "reconvergence" then this sounds about correct
04-26-2024 03:25 AM
Hello,
can you post the output of:
show spanning-tree mst
Maybe we can spot something...
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