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RSTP and MSTP in a Cisco-NonCisco Hybrid Network



I am designing a network for industrial purpose, and I have some doubts designing the Rapid/Multiple Spanning Tree Redundancy.

My two core switches are Cisco Catalyst 3750G but all the other devices in the network are Non-Cisco. If you take a look in the drawing I attach you will see the topology. Each ring is planned to have around 30-35 switches

- The core switch 1 is configured as root bridge (prio 4096) and the switch 2 as backup root (prio 8192). All the other switches have prio 32768.

- Each of the links shown in the diagram (red,blue,black) are trunk ports. Each ring has 4 different VLANs and one VLAN (VID 100) shared by both rings.

- The Non-Cisco devices can only work with RSTP. The colors are just to distinguish between physical rings.

- Core 1 and Core 2 are in different buildings. That's the reason for the cross-connections.

My question is, how do I have to configure both Cisco to make them able to see Ring A as a single RSTP domain and Ring B as another single RSTP domain? I am pretty new with this issues and I am getting some problems understanding the operation of both protocols together.......

thanks a lot for your help!

best regards,


2 Replies 2

Mohamed Sobair
Rising star
Rising star


Since you have 4 different Vlans on each building, then each ring will have its Own RSTP Domain for those VLans.

Only vlan 100 (The shared Vlan), would have singl RSTP domain between both rings.

Let me know if this answers your question,



Hi Mohamed,

thanks a lot for your answer! And sorry for my delayed answer. I was on a business trip...

So, if I understood well, by activating MSTP in the Core Catalysts, they will do everything automatically, right? Or any VLAN configuration has to be made in the trunk ports (permitted VLANs,...)

Since both Rings are connected via both Catalyst there won't be any risk of mixing both RST domains, right?

Thanks again for you help!

Best regards,


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