Fabric Connect Load balance among more than two paths, possible?

[difan]

Quick question:

Does two Backbone VLANs mean I can only load balance between two PATHs? 

For example, in scenario that I have three BCBs sw1, sw2 and sw3 and two BEBs sw4 and sw5. Sw4 and sw5 has connections to all three BCBc but not between each other. When users/devices on sw4 communicate to users/devices on sw5 (on the same VLAN/I-SID), can traffic take all three paths/BCBs, or will it take only sw1 and sw3 (for the two Backbone VLANs, one picking the lowest system ID sw1 and another picking the highest system ID sw3?

Thanks!

Difan

[difan]

@EXTR_Paul @Shaja I have been thinking. Is the BVLANs only for BUM traffic? And Once the destination MAC address is learned (meaning that the destination BEB is known for the Customer MAC), it will use all available paths for sending the packet? Thanks. 

[WillyHe]

It will always take the shortest path, when there are equal cost paths, then traffic is load balanced.

[difan]

Hi Willy, let's say that the destination c-MAC is learned and it is on a BEB with a b-MAC. There are three equal-cost paths to the b-MAC. Can it load balance on all three paths? Is there a command to list all equal-cost paths to a c-mac? Thanks!

[EXTR_Paul · Accepted solution]

In an SPBm network ALL TRAFFIC will take the shortest path on a physical links between BCBs and BEBs.

However, in a situation where there is a symmetrical equal path between BCBs and BEBs traffic will get balanced across the links. 

However, the necessity to balance over more than 2 BVLANs is redundant  because the equal path vector can only ever be over two links.   Balancing over more than 2 BVLANs really gives you nothing.