MST Region Change

[D@1984]

Hi,

do I need to reboot a switch for changes to apply after I change region and MST VLAN mapping.

Thanks

[Enes Simnica]

hello D@1984 and no, u don’t need to reboot the switch. Because changes to MST region configuration (like name, revision, VLAN-to-instance mapping) are applied immediately after u exit configuration mode. However, the switch will recalculate the MST topology, which can cause a temporary spanning-tree convergence event.

So while a reboot isn’t required, be aware that u might see momentary traffic disruption during the re-convergence!!!!!

https://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli_rel_4_1/Cisco_Nexus_5000_Series_Switch_CLI_Software_Configuration_Guide_chapter12.pdf

hope it helps, and PEACE!

-Enes

[D@1984]

thank you. does joining switches to the rest of region also cause some flaps in interfaces ,while doing recalculation STP paths, even though the root of region stay the same?

Thanks

[Enes Simnica]

u r absolutely welcome D@1984. and Yes, even if the root stays the same, adding switches to the MST region can cause brief STP recalculations and interface flaps (port transitions between blocking/forwarding). This happens because MSTP must sync the new topology across all switches in the region, which takes a few seconds. And if u wanna minimize impact, plan changes during a maintenance window (which is the best option man, believe me looool, i have caused outages on a live production with STP, and it is not funny HAHAHA) 

and consider this also : Use spanning-tree mst pre-standard  (if compatible and if u wanna dive deeper) to speed up convergence, or tweak timers cautiously (but only if you fully understand the trade-offs).

hope it helps man, and all the best.....

-Enes

[Enes Simnica]

also D@1984, dont forget to use a lot of show commands while configuring and troubleshooting MST (STP in general) because u will see how STP works behind the scenes,, u will see ports going from one state, like Learning to forwarding and stuff, IT IS SOOOOOO MUUUUUCH FUUUUUUN!!!  SO have fun my Cisco friend!

[MHM Cisco World]

MHM

[paul driver]

Hello D@1984 
Not sure why you are opening up additional posts on the same subject, please close off the others beforehand or mark them accordingly or just reply with an further query?
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