Q 1 ) d
Explanation-The root port is the port with the lowest cost to reach the root bridge.
Q 2 ) a, c, e,
Explanation-The three components that are combined to form a bridge ID are bridge priority, extended system ID, and MAC address.
Q 3) d
Explanation-The BPDU has three fields; the bridge priority, the extended system ID, and the MAC address. The extended system ID contains 12 bits that identify the VLAN ID.
Q 4) c
Q 5) c , d
Explanation-Switches learn MAC addresses at the learning and forwarding port states. They receive and process BPDUs at the blocking, listening, learning, and forwarding port states.
Q 6) a
Explanation:Although the spanning-tree vlan 10 root primary command will ensure a switch will have a bridge priority value lower than other bridges introduced to the network, the spanning-tree vlan 10 priority 0 command ensures the bridge priority takes precedence over all other priorities.
Q 7 ) c
Explanation- When all switches are configured with the same default bridge priority, the MAC address becomes the deciding factor for the election of the root bridge. All links on the same VLAN will also have the same extended system ID so this will not contribute to determine which switch is the root for that VLAN.
Q 8) a
Explanation: If switch access ports are configured as edge ports using PortFast, BPDUs should never be received on those ports. Cisco switches support a feature called BPDU guard. When it is enabled, BPDU guard will put an edge port in an error-disabled state if a BPDU is received by the port. This will prevent a Layer 2 loop occurring. PVST+ is an implementation of the Spanning Tree Protocol. The extended system ID is a mechanism of including VLAN ID information in the bridge ID (BID) for each VLAN.
Q 9) d
Explanation: MST is the Cisco implementation of MSTP, an IEEE standard protocol that provides up to 16 instances of RSTP and combines many VLANs with the same physical and logical topology into a common RSTP instance. Each instance supports PortFast, BPDU guard, BPDU filter, root guard, and loop guard. STP and RSTP assume only one spanning-tree instance for the entire bridged network, regardless of the number of VLANs. PVST+ provides a separate 802.1D spanning-tree instance for each VLAN that is configured in the network.
Q 10) d
Explanation: Switch ports that connect to host devices are RSTP edge ports and will immediately transition to the forwarding state when the port is enabled.
