Hi!
@JaxHT wrote: My purpose is to limit spanning tree to the Aruba 5406R zl2 stack (new site) by using L3 link via RAGG port. The BAGG port with untagged vlan is used for routing point-to-point; the other subnets are tagged for inter-vlan routing on this new site.
The point is that ArubaOS-Switch doesn't support RAGG ports (Routed LAGs)...so your option (your scenario) is to have a Port Trunk (a LAG) properly tagged or untagged with a particular VLAN Id (used to just as to Point-to-Point transport) and then use for that VLAN Id a particular strict IP addressing (say a /31) and apply static route on your Aruba 5400R zl2 VSF stack to networks behind the other L3 peer Switch...on the L3 peer Switch (where the Port Trunk - LAG - terminates) apply the same approach for traffic in the opposite direction.
You need to divide/separate these two joining networks? I believe that bpdu-filter should give you an help BUT I'm not sure you can apply this spanning tree bpdu filtering approach (keeping spanning tree topologies separated by means of interfaces not partecipating in spanning tree by being always in forwarding mode and filtering BPDUs)...why? because you're applying (or you are going to apply) it against a Port Trunk logical interface (made of two or more aggregated links, NonProtocol or LACP doesn't matter)...it it is a single link interconnecting two networks...the bpdu filtering approach works for sure...with aggregated links I don't believe so (I fear it is mutually exclusive).
Edit: or maybe I'm wrong and spanning tree bpdu-filter can be applied also on Port Trunking logical port by applying it on its member ports (see here the example).