MST Questions

Question 1

Explanation

Instead of using Per-VLAN Spanning Tree (PVST) or Rapid PVST which runs a separate STP instance for each active VLAN (there will have 20 STP instances for 20 VLANs), Multiple Spanning Tree (MST) maps multiple VLANs into a spanning tree instance, thereby reducing the number of spanning-tree instances needed. MST also reduces switch resources and managerial burdens.

Question 2

Explanation

Besides two MST instances 1 & 2, Instance 0 is a special instance for a region, known as the Internal Spanning Tree (IST). The IST always exists on all ports; you cannot delete the IST. By default, all VLANs are assigned to the IST. All other MST instances are numbered from 1 to 4094. The IST is the only STP instance that sends and receives BPDUs. All of the other MSTI information is contained in MST records (M-records), which are encapsulated within MST BPDUs.

Note:
+ The Common Spanning Tree (CST) interconnects the MST regions and any instance of 802.1D and 802.1w STP that may be running on the network
+ A Common and Internal Spanning Tree (CIST) is a collection of the ISTs in each MST region.

Question 3

Explanation

Unlike Per-VLAN Spanning Tree (PVST) which maintains a spanning tree instance for each VLAN configured in the network, Multiple Spanning Tree (MST) maps multiple VLANs into a spanning tree instance, thereby reducing the number of spanning-tree instances needed. MST also reduces switch resources and managerial burdens.

Question 4

Question 5