MST ring diameter

[2044418Puts]

Hello,

One of our clients is running MST on a ring with a diameter of 40 switches. Up until now everythings works fine. Our client wants to expand this even more with a couple of extra switches. I have not much realworld experience with MST. So I have the following questions:

- What is the maximum ring diameter?

- Is it suggested to break the ring between the switches which are the farthest away from the root and to connect those switches back to the root, so I essentially create two rings of 20 switches instead of a larger 40-45 switches ring?

Thanks!

Regards,

Armand

[Peter Paluch]

Hello Armand,

- What is the maximum ring diameter?

If all switches are in a single MST region, the maximum diameter is by default 20 hops. This can be changed on the MSTI0 root (ideally, on all switches) using the spanning-tree mst max-hops commands. I stronly suggest incrementing this value for your customer's network, as its diameter is 40 currently.

- Is it suggested to break the ring between the switches which are the  farthest away from the root and to connect those switches back to the  root, so I essentially create two rings of 20 switches instead of a  larger 40-45 switches ring?

I am not sure about this one. A common sense would indicate that smaller rings are better but then again, the diameter is not really significantly decreased and the MSTP operation does not seem to be substantially changed. Perhaps somebody could add his own suggestion here - I would be very thankful for it.

Best regards,

Peter

[2044418Puts]

Anyone any ideas about the maximum recommended/supported ring size while using MST?

Thanks!

Regards,

Armand