[c-nsp] Question about Multiple Spanning Tee (MST)

[Clinton Work]

Generally, you want to split your vlans between the MST instances based 
upon administrative control.  All the vlans in a particular instance 
have to share the same spanning tree topology.  I would put vlans into 
difference instances based upon the following. 

a) in-band mgmt vlan
b) splitting vlans into two or more groups which will have different 
blocking points in order to implement load sharing
c) groups of vlans where you want to have independent control so you can 
change the blocking point without affecting the MST instances.  This 
could be grouped based upon departments or vlan function  (Internet, 
DMZ,  Enterprise, ...).  You may have a requirement to have red and blue 
vlans take diverse links (if possible) across the switched network.  

I would come up with a MST instance plan that covers all the vlans you 
might want to use so your not modifying the MST configuration all the 
time.  

Clinton.

Andy Saykao wrote:
> Hi All,
>  
>  For example:
>  
> Option 1/ If we have 500 vlans, do we split them into two instances
> (instance 1 vlan 1-250 and instance 2 vlan 251-500). 
>  
> Options2/ Or would you split the vlans up based on their business
> requirements.
> Eg: vlan 1,10,100 Marketing-related vlans, vlan 2,20,200 Sales-related
> vlans - therefore create instance 1 vlan 1,10,100 and instance 2 vlan
> 2,20,200???
>  
> Secondly, what if you went with option 2, and added a new vlan into
> Marketing (eg: vlan 1000). Would you have to manually update the
> spanning-tree mst config on all MST switches to include the new vlan in
> the instance??? 
>  
> Thanks.
>  
> Andy
>  
>
>   
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Clinton Work
Airdrie, AB