正解:B
In a vPC (Virtual Port-Channel) configuration, multicast traffic is handled based on the vPC design and operational rules. When a host sends traffic to a multicast group, the vPC switches determine the forwarding path based on the source and the vPC domain configuration. If multicast traffic is received on a vPC member port, such as Po10 on Switch1, the traffic is typically forwarded out on all ports that are part of the same VLAN and have receivers interested in the multicast group, which includes Po1 and Po20 in this case. This ensures that the multicast traffic reaches all intended recipients across the vPC domain.
References: For a comprehensive understanding, the Cisco documentation on "Multicast forwarding in vPC based on location of the source" provides detailed scenarios and explanations on how multicast traffic is forwarded in a vPC environment1. Additionally, the "Cisco Nexus 9000 Series NX-OS Multicast Routing Configuration Guide" offers insights into the configuration and behavior of multicast routing on Nexus switches, which can be applied to understand the vPC behavior with multicast traffic