Practice Q's - MST Flashcards
Which of the following statements best describes the result of issuing the instance 3 vlans 7 command?
A. VLAN 7 is mapped to MST instance 3.
B. VLAN 7 is mapped to switchport 3.
C. VLAN 7 is mapped to three MST instances.
D. Seven VLANs are mapped to MST instance 3.
Answer: A
Explanation:
When the instance 3 vlans 7 command is issued, the virtual local area network (VLAN) 7 is mapped to Multiple Spanning Tree (MST) Protocol instance 3. MST, which is defined by the 802.1s standard, maps a distinct group of VLANs to one STP instance. Multiple STP instances can be used with MST. The Cisco implementation of MST supports 256 instances. However, each instance must support a different group of VLANs because each VLAN can only be mapped to one instance.
To map one or more VLANs to an MST instance, issue the instance instance-ID vlans vlan-range command, where ID is the number of the MST instance and vlan-range is the VLAN or VLANs that should be mapped to the instance. For example, the command instance 1 vlans 14-16,99 maps VLANs 14 through 16 and VLAN 99 to MST instance 1.
The instance 3 vlans 7 command will not map VLAN 7 to switchport 3. The instance vlans command cannot be used to map multiple instances to a single VLAN. Each VLAN can only be mapped to one instance. When the instance 3 vlans 7 command is issued, only a single VLAN will be mapped to MST instance 3.
