Wired Intelligent Edge

Customer is connecting their Access switch to two Distribution switches via trunk links with RPVST in current network. We are working with them to convert their current Distribution switches from Cisco 6509 to Aruba CX 6405 using VSX. Customer does understand the recommended design is to use LAG between Access and Distribution when using VSX. But since they have too many Access switches and they don't want to change their Access configurations in this migration, they ask if it's ok to keep current trunk links between Access and two VSX switches. Does anyone see any issue here?

Assuming we'll go with this design, now since RPVST configuration will keep the same between two VSX switches (like priority) as per VSX guide, how will RPVST primary and secondary be elected in this scenario? Will one of the ports be blocked so that the two VSX switches will be running as active-standby on L2?

Thank you!

Hi

In my eyes there is no issue with it apart from the fact that you will not have full bandwidth available (redundant links are blocked). 

VSX switches act as one bridge in the spanning-tree. So there is no active/prmary and standby/secondary in this context. On the access switch therefore you will see two connections which have the same upstream bridge. Given that your VSX cluster is closer to the root bridge (or perhaps IS the root bridge) than the access switches are, a link on the access switch will be blocked, not on the VSXs. On the access switch the link with the higher port id if I'm not mistaken will be blocked.