Connecting FabricPath domain with STP domain

[Mukund Sandur]

Hi,

I have a FabricPath domain consisting of 6 switches -- 2 nos Nexus 7010 and 3 nos of 5596 switches. All the six switches are part of FP domain and VLAN 10 is the FP VLAN.

I want to connect two 6509 switches to FP domain where one 6509 will connect to one Nexus 7k and other 6509 to other Nexus 7K. Both 6509 switches are part of single STP domain with VLAN 10.

I am aware that FabricPath egde switches must be configured as STP root for all FabricPath VLAN ie VLAN 10 in my case. Since multiple FabricPath edge switches connect to same STP domain, my query is whether both or any one of the FP edge Nexus7k should be configured as root.

Cisco documentation says that make sure that those edge switches use the same bridge priority value. What does it mean exactly. What is the recommended configuration for connecting same STP domain to multiple FP edge switches.

Attaching herewith sample diagram for reference.

[allan.thomas]

Hi,

My understanding for configuring the same bridge priority on the Fabric Path switches is to ensure that the FabricPath network presents as a single bridge to all the classical Ethernet connected switches, in your case both the Cisco 6509s. This ensures a loop free topology for the same STP domain spanning both 6509s connected to the Fabric Path network, thus both CE devices should be designated interfaces. If they're not designated ports for the active STP domain they will be pruned until the Fabric Path terminating switch stop receiving the superior BPDUs. Not sure if that really answers your question without being able to replicate the setup to prove the theory.

Regards
Allan

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