With the Cisco RPVST+, which of the following action(s) does a switch take to identify which VLAN is described by a BPDU? (Choose three answers.)

With the Cisco RPVST+, which of the following action(s) does a switch take to identify which VLAN is described by a BPDU? (Choose three answers.)

• Adds a VLAN tag when forwarding a BPDU on trunks
• Adds the VLAN ID in an extra TLV in the BPDU
• Lists the VLAN ID as the middle 12 bits of the System ID field of the BPDU
• Lists the VLAN ID in the System ID Extension field of the BPDU

Explanation: The Cisco Rapid Per VLAN Spanning Tree (RPVST+) creates one spanning tree instance per VLAN. To do so, it sends BPDUs per-VLAN. Each switch identifies itself with a unique Bridge ID (BID) per VLAN, made unique per-VLAN by adding the VLAN ID to the system ID extension 12-bit field of the BID. RVPST also adds a new Type-Length Value (TLV) to the BPDU itself, which includes a place to list the VLAN ID. Finally, when transmitting the BPDUs over VLAN trunks, the switch uses a trunking header that lists the VLAN ID (a practice sometimes called tunneling in 802.1Q.) The receiving switch can check all three locations that list the VLAN ID to ensure that they all agree about what VLAN the BPDU is describing. Of the four answers, the three correct answers describe the three actual locations in which RPVST+ lists the VLAN ID.