STP Dispute

This topic is to discuss the following lesson:

Hi,
Cisco virl is must for this lab ?
Which image you are using for this switch

Thanks

Hi,
What is this mac ‘0180.c200.0000’
Thanks

Hello Sims

All 802.1q traffic (spanning tree traffic) is destined for the 0180.c200.0000 multicast MAC address. If this is blocked, then STP traffic will be blocked.

I hope this has been helpful!

Laz

So its a In-build Feature or Mechanism right - We don’t enable them ?

Hello Mohit

Yes, STP Dispute is a built in feature, and requires no configuration. Actually, it cannot even be disabled.

I hope this has been helpful!

Laz

Hello Guy,

I’m currently doing some labs related to MSTP and there is something that I need to investigate :
On S8, I just do a simple “int vlan 2020; shutdown”, following this one, I can see many flap on other vlan interfaces so I was suspecting some events on my mstp topology and with the debug on S7 :

S7#
*May 23 10:25:39.435: %AMDP2_FE-6-EXCESSCOLL: Ethernet0/3 TDR=0, TRC=0
S7#
*May 23 10:25:43.373: %VRRP-6-STATECHANGE: Vl2020 Grp 202 state Master -> Backup
S7#
*May 23 10:25:43.690: MST[0]: Et0/1 disputed
*May 23 10:25:43.690: MST[0]: Et0/1 state change forwarding -> blocking
*May 23 10:25:43.690: MST[1]: Et0/1 state change forwarding -> blocking
*May 23 10:25:43.690: MST[1]: Et0/1 disputed
*May 23 10:25:43.690: MST[0]: sending proposal on Et0/1
*May 23 10:25:43.690: MST[1]: sending proposal on Et0/1

I understand thanks to your course why I see the dispute message in my debug (after my action, BPDU received from S8 we can see port role changed from root to Designated) but I still don’t understand why this simple action on vlan interface number 2020 caused this mess.
Vlan 2020 belongs to MSTI 2. We can see the first notification is the vrrp role changement which is as expected.

Any clue on this one ?

Yoann
MSTP_SiteC_eveng