Large RSTP ring

[albuscala]

Hello,

Is it possible to make a large redundant ring with switches using RSTP protocol, such as a ring with 500 switches for example ? What would be the limitation cause ?

[acampbell]

I can not find much in Cisco about deploying a large RSTP ring configuration.

On another vendor sit it says that RSTP can not support ring of more than

31 switches.

I think 31 in a ring is not very ressilliant

I would be looking at deploying a partial mesh at least.

Regards

Alex

[wasmer_anne]

It's more the re-convergence time after a link / switch failure that would be the problem with a very large RSTP diameter; the limitation of having 500 switches within a single RSTP domain would be the possible transitional black holes due to re-convergence. The other limitation could be sub-optimal path forwarding with default port costs. Another limitation is manageability and security.

I'm guessing it would depends on the VLANs structure, the physical topology and the position of the Root bridges.

500 + switches on one VLAN with all settings left to default would be a network meltdown...

[albuscala]

Thank you for your response.

What if the application accepts a long time recovery of few seconds ? Modifying the timing parameters, would there be a problem to make a large RSTP ring with so much switches ?

Maybe it exists a simulator that could be useful to try such a configuration ?

[acampbell]

Hi,

Here is the link to the Cisco perspective on RSTP

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml

HTh

Alex

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