06-19-2024 11:56 PM
Hello,
I have a question regarding MSTP implementation. We are in the migration process to replace a standalone 6509 by two Nexus 9K switches.
We used to have MSTP running between the 6509 (root) site A and the nexus SFP site B. All others switches are in pvst. We have dedicated fibers connecting the switches with different vlan for each client. I was using MSTP in order to do that, but there might be a better solution ?
Attached is the layer 2 topology of the current situation, partly migrated some fibers to the Nexus and mstp in a messy state. I would like to migrate the final fibers of client C (in green) to the top Nexus and switch on the link between the 6509 and the Nexus (link in blue).
Could I configure MSTP only between the Nexus SFP of site A/B ? And keep the 6509 in pvst ? Which one of the Nexus should be root ?
Looking forward to any advice.
06-20-2024 04:37 AM
why you dont need to run MST in c6K ?
run multi STP modes , hmm it not optimal
MHM
06-21-2024 04:04 AM
Should I run mstp on all the switches?
06-22-2024 05:39 AM
1- run MST in all SW that what I suggest
2- if you want to run PVST + MST then see below how we can config SW that run PVST to simulate MST
MHM
06-25-2024 01:52 AM
Did you read the link ?
there are two cases be careful the priority not always higher and it not for all VLAN
please be careful and read the link I share more than one time, if you have Q please ask before run any command
With such a topology (a mixture of MST and non-MST regions), the root bridge of CIST is in one of two places:
PVST simulation runs seamlessly with two critical rules:
06-25-2024 03:32 AM
Hello @MHM Cisco World
PVST+ simulation is something you do need to be aware of however it will NOT negate having mst/pvst+ stp domain, they will indeed work together you just need to be aware of the "gotchas" doing so.
06-25-2024 04:04 AM
friend please check Link I share, I know what I talking about mix PVST+MST can lead to pvst_inc and BLK port.
MHM
""Often, MST regions are connected to other domains - Per VLAN Spanning Tree Plus (PVST+) or rapid-PVST+ regions. These switches that run PVST+ (or rapid) cannot process MST-type Bridge Protocol Data Units (BPDUs). For this reason, there must be a backward-compatibility mechanism that runs so that these two domains can interact with each other seamlessly. This is what PVST simulation addresses and achieves.
This simulation must be run only on boundary ports - these are ports that are directly connected to the PVST+ domain switches. The receipt of a Shared Spanning Tree Protocol (SSTP) BPDU on the port of a switch that runs MST causes the PVST simulation mechanism to trigger.""
06-25-2024 05:08 AM - edited 06-25-2024 05:09 AM
Hello
@MHM Cisco World wrote:
friend please check Link I share, I know what I talking about mix PVST+MST can lead to pvst_inc and BLK port.
PVST+ simulation isnt something you enable, its something you need to be aware of and negate from happening when you have to connect pvst+ stp domains to mst stp domains
Which means you CAN connect these two stp domains together
06-25-2024 05:13 AM
Which means you CAN connect these two stp domains together <<- did I mention different in my previous comment ?
I mention he must be careful never mention he can not mix
and again I suggest use same STP mode if he can
MHM
06-26-2024 10:05 PM
Thank you for taking the time to help out.
The issue running MST in all SW is that the RJ45 Nk9 in site A have loads of VLANs that are not needed on other sites.
If I run MST + PVST, how would you configure MST ? MST on Nk9 SFP on site A and B and all other switches on PVST ?
Regards
06-27-2024 03:51 AM
the MST is config with two instance only no need more
each instance contain half of VLAN available in SW even VLAN not use new but can use in feature.
MST dont send like PVST using VLAN tag so it dont matter if the VLAN is use in one SW and dont use in other SW
anyway to help you I run lab and show you case
using MST
using mix MST + PVST
MHM
06-24-2024 04:34 AM
Hello
If you want to run mst & pvst domains then have the Nk9 in site B to be the root for the whole STP estate, just make sure on the PVST+ switches the stp priority's for all vlans are higher(less preferred) then the MST domain.
06-26-2024 09:59 PM
Thank you for taking the time to help out on my case.
Should I configure the Nk9 Site B and Site A on MST ? and the others swtiches can stay in pvst ?
The problem running mst on all the swiches is that few vlans are used between sites but each site has quite a lot of VLANs, especially the Nk9 on site A and B.
06-27-2024 02:07 AM
Hello,
I have not followed the entire thread, but I am just thinking why not simply use MST on all switches, and then manually prune the Vlans you don't need ?
06-27-2024 03:44 AM
Hello
@Georg Pauwen wrote:
why not simply use MST on all switches, and then manually prune the Vlans you don't need ?
MST is per instance not per vlan as such vlans, you should not be pruning any vlans off any trunks
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