Hi Parnassus, Thank you that question pointed me in the right direction! I know that the root bridge is managing MST0 and that my network has spanning tree flapping, so I checked the root bridges and was really astounded that my root settings are vanished.
This explains why they never become the root. I configured the spanning tree settings and after a few seconds everything works!
Thank you very much! Sometimes you need to talk with somebody to get the right idea!
Best wishes
Michael
Original Message:
Sent: 11/19/2024 9:18:00 AM
From: parnassus
Subject: RE: Aruba-CX mstp spannning-tree instances
Hi Micheal! great. One of your questions captured my curiosity now: "Or is this a way to keep spanning-tree calm when you add a new vlan?", does the question mean that when you create a new VLAN and you assign it to a specific ST instance then a recalculation (maybe with a ST disruption?) is triggered? I understood it correctly your worry?
Original Message:
Sent: Nov 19, 2024 07:52 AM
From: Signor Mic
Subject: Aruba-CX mstp spannning-tree instances
Hi Parnassus,
thanks for the link and your comment! I know of similar examples to the one
shown in the lab.
I find it difficult to apply such examples to my network because I currently
have around 40 VLANs and the number is still growing.
But I think that the load balancing in the network can be further
distributed by many instances... At the moment I only have two instances.
Maybe I should first rebuild the example and see if I can learn more from
it.
Kind regards
Michael
Original Message:
Sent: 11/19/2024 7:16:00 AM
From: parnassus
Subject: RE: Aruba-CX mstp spannning-tree instances
Hi! generally speaking an MSTP approach with multiple ST instances is required when a network topology is (natively) not loop-free by design (because there are redundant links necessarily forming undesired loops) but it is required that that network to be loop-free from the VLANs stanpoints, so requiring different spanning tree topologies (and this requires to define MST Primary and Secondary roles, to be used in different core switches). For sure, using a similar approach, results into a "balancing" cause/effect, I personally don't know if this approach (say, having just two or more ST instances versus having a lot more of ST instances) could be primarily used to expect a sort of gain in ST performance (I mean, in terms of expected calculation performance's gain), clearly the MSTP with two or more ST instances is used when the topology requires that. Probably there is a more technical type of answer that could be given (also from the point of view of how an ArubaOS-CX switch calculates an ST topology). See here.
Original Message:
Sent: Nov 18, 2024 10:57 AM
From: Signor Mic
Subject: Aruba-CX mstp spannning-tree instances
Hello all,
I'm thinking about mstp spanning-tree instances. Would it be helpfull to split all vlans over maybe 8 or more instances?
For example:
spanning-tree instance 1 vlan 1-99,600-699,1200-1299,1800-1899,2400-2499,3000-3099,3600-3699
spanning-tree instance 2 vlan 100-199,700-799,1300-1399,1900-1999,2500-2599,3100-3199,3700-3799
spanning-tree instance 3 vlan 200-299,800-899,1400-1499,2000-2099,2600-2699,3200-3299,3800-3899
spanning-tree instance 4 vlan 300-399,900-999,1500-1599,2100-2199,2700-2799,3300-3399,3900-3999
spanning-tree instance 5 vlan 400-499,1000-1099,1600-1699,2200-2299,2800-2899,3400-3499,4000-4095
spanning-tree instance 6 vlan 500-599,1100-1199,1700-1799,2300-2399,2900-2999,3500-3599,
What are you thinking? Does spanning-tree needs to much CPU for the spanning-tree calculation? Or is this a way to keep spanning-tree calm when you add a new vlan?
Greetings