Hello,
I have a question regarding the way a root port ist choosen.
Imagine the following Szenario…
Two CRS309-1G-8S+ are connected via SPF1 and SPF2 via DAC with 10G fdx link speed. Active LACP ist enabled on both switches for SPF1 and SPF2. But the same two CRS309-1G-8S+ are also connect via port SPF6 with 10G fdx. LACP for SPF6 is passive on both switches. In reality there is a device in between the two SPF6 ports, but that device is layer 2 transparent… so for those two switches it seems like they were also directly connected on port SPF6. They will receive each others BPDUs on port SPF6.
Now RSTP kicks in, the LACP bond (SPF1+SPF2) and the SPF6 will be detcted as a loop. Let’s say switch A has bridge priority 2000 and switch B has bridge priority 4000. The LACP bond will not have a lower path cost than the single 10G port because bonding two 10G ports doesn’t reduce the path cost.
My question will the LACP bond “win” the RSTP selection? And which switch will put his SPF6 in alternate state?
Thanks.
Your, Barungar