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Metro Ethernet Spanning Tree

Dustin Flint
Level 1
Level 1

I am trying to determine the best option for Implementing spanning tree on Metro Ethernet. Essentially I need each customer bridge-domain/vlan to be in its own instance. A few people have recomended using MST. My question is why? If each customer is in its own instance and there could be 10-15 customers, what is the benefit of using MST over RSTP? I am guessing there are pros/cons of going either way.

1 Accepted Solution

Accepted Solutions

Dustin Flint
Level 1
Level 1

Due to MST only allowing 16 instances per region, we have opted to go with rapid per vlan spanning tree

View solution in original post

4 Replies 4

Peter Paluch
Cisco Employee
Cisco Employee

Hi Dustin,To clarify - are you going to implement 802.1ad Q-in-Q, or do you intend to simply run separate VLANs, and receive untagged traffic from customers?

Best regards,
Peter

 

Yes, it is a Q-in-Q, because I cannot dictate which vlans customers can use. So customers may have overlapping vlans and IP address schemes. Here is an example of a customer port on and ME3800:

 

interface GigabitEthernet0/2
   description Customer 1
   switchport trunk allowed vlan none
   switchport mode trunk
   mtu 1504
   service instance 1 ethernet
       encapsulation untagged , dot1q 1-4094
       l2protocol tunnel cdp stp vtp dtp lldp
       bridge-domain 500

One last question as I just thought of this. If we have more than 16 customers, we cant use mst in which each customer has its own instance. Since each MST region is limited to 16 instances.

 

So if we have more than 16 customers we would have to use rapid pvst. I don’t know that having more than 1 region would help us, as I need the ability to have some vlans go to every site.

Dustin Flint
Level 1
Level 1

Due to MST only allowing 16 instances per region, we have opted to go with rapid per vlan spanning tree

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