PrepAway - Latest Free Exam Questions & Answers

Which of the following commands can you issue to enable RSTP? (Select 2 choices.)

Which of the following commands can you issue to enable RSTP? (Select 2 choices.)

A. spanning-tree mode mst

B. spanning-tree mode pvst

C. spanning-tree mode rapid-pvst

D. no spanning-tree mode

Explanation:

You can issue the spanning-tree mode mst command or the spanning-tree mode rapid-pvst command to enable Rapid Spanning Tree Protocol(RSTP). RSTP, which is defined in the Institute of Electrical and Electronics Engineers (IEEE) 802.1w standard, is used to improve the slow transition of a Spanning Tree Protocol (STP) port to the forwarding state, thereby increasing convergence speed. A switch port will pass through the following RSTP states:
– Discarding
– Learning
– Forwarding

When RSTP is enabled on a switch port, the port first enters the discarding state, in which a port receives bridge protocol data units (BPDUs) and directs them to the system module, however, the port neither sends BPDUs nor forwards any frames. The switch port then transitions to the learning state, in which it begins to transmit BPDUs and learn addressing information. Finally, a switch port transitions to the forwarding state, in which the switch port forwards frames. If a switch port determines at any time during the RSTP state process that a switching loop would be caused by entering the forwarding state, the switch port again enters the discarding state, in which the switch receives BPDUs and directs them to the system module but does not send BPDUs or forward frames.
The spanning-tree mode mst command enables Multiple Spanning Tree (MST), which uses RSTP. MST, which is defined in the IEEE 802.1s standard, is used to enable multiple spanning trees for groups of one or more virtual LANs (VLANs).
The spanning-tree mode pvst command enables PerVLAN Spanning Tree Plus (PVST+), which uses STP, not RSTP. PVST+, which is defined in the IEEE 802.1D standard, creates a separate spanning tree instance for each VLAN and can be used with 802.1Q encapsulation. By contrast, PVST can only be used with InterSwitch Link (ISL).
The spanning-tree mode rapid-pvst command enables RapidPVST+, which uses RSTP. RapidPVST+, which is defined in the IEEE 802.1w standard, combines the rapid transition of ports by RSTP with the creation of spanning trees for each VLAN by PVST+.
The no spanning-tree mode command is not used to enable RSTP. Rather, it is used to configure a switch with the default switch mode, PVST+.

Reference:
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3560/software/release/12-2_25_see/command/reference/cr/cli3.html#wp1946050
https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/24248-147.html#mst_config_region


Leave a Reply