When you connect two Cisco devices through 802.1Q trunks, the devices exchange spanning tree BPDUs on each VLAN that is allowed on the trunks.
Which two statements are correct about the BPDUs that are sent on the native VLAN of the trunk? (Choose two.)
Click on the arrows to vote for the correct answer
A. B. C. D. E.AE.
When two Cisco devices are connected through 802.1Q trunks, the devices exchange spanning tree BPDUs (Bridge Protocol Data Units) on each VLAN that is allowed on the trunks. BPDUs are used to determine the root bridge and to create the Spanning Tree topology to prevent loops in the network.
Regarding the BPDUs sent on the native VLAN of the trunk, the correct statements are:
A. BPDUs are sent to the reserved IEEE 802.1D spanning tree multicast MAC address (01-80-C2-00-00-00). E. BPDUs are untagged when they are sent.
Explanation: The native VLAN is the VLAN that is not tagged on the trunk. By default, VLAN 1 is the native VLAN.
A. BPDUs sent on the native VLAN are sent to the reserved IEEE 802.1D spanning tree multicast MAC address 01-80-C2-00-00-00. This is the destination MAC address used by all 802.1D-compliant devices to receive and process BPDUs.
B. The IEEE 802.1Q standard does not specify a unique MAC address for the spanning tree protocol. Instead, the same MAC address (01-80-C2-00-00-00) is used for both 802.1D and 802.1Q-compliant devices.
C. The SSTP (Shared Spanning Tree Protocol) is a proprietary protocol developed by Microsoft for use in Windows networks. It is not related to the IEEE 802.1D or 802.1Q standards, and BPDUs are not sent to the SSTP multicast MAC address.
D. BPDUs are not tagged with the VLAN number when they are sent on the native VLAN. This is because the native VLAN is untagged on the trunk, so there is no VLAN tag to include in the BPDU.
E. BPDUs sent on the native VLAN are untagged, as mentioned above. This is because the native VLAN traffic is sent untagged on the trunk, and BPDUs are part of the native VLAN traffic.
In summary, BPDUs are sent untagged on the native VLAN of a trunk to the reserved IEEE 802.1D spanning tree multicast MAC address 01-80-C2-00-00-00.