MST Flashcards
In MST, what does IST refer to?
Internal spanning tree–the area within a MST region. It resides on instance 0, and sends the actual MST BPDUs.
Briefly describe MST.
Multiple spanning tree allows multiple VLANs to be mapped to instances, allowing the control of PVST+ without the strain on the CPU.
What must the switches in a MST region agree upon?
MST region name, VLAN-instance mapping, and MST configuration number.
Which protocol defines MST?
802.1s.
In MST, switches are divided into ___.
Regions.
How many instances can exist in a MST region?
16, 0-15.
When CST interacts with MST, what instance is it placed into?
0.
In MST, when a VLAN is not assigned to an instance, what will it be placed into automatically?
0.
In MST, which instance will BPDUs actually be sent on?
0.
How many VLANs can be mapped to MSTI 0?
As many as you want, 0-4096.
A network engineer is setting up a new switched network. The network is expected to grow and add many new VLANs in the future. Which Spanning Tree Protocol should be used to reduce switch resources and managerial burdens that are associated with multiple spanning-tree instances?
MST
When two MST instances (MST 1 and MST 2) are created on a switch, what is the total number of spanning-tree instances running on the switch?
3
Define MST
Defined in IEEE 802.1s, a specification for multiple STP instances when using 802.1Q trunks
What does *MST* stand for?
Multiple Spanning Tree
What is *MST*?
MST is IEEE’s answer to Cisco’s Per-VLAN STP implementation. With MST, you are able to bundle VLANs together in instances, similar to the per-vlan system except using lesser resources.
What configuration command would set up *MST*?
- Sw1(config)# spanning-tree mode mst
- Sw1(config)# spanning-tree mode configuration
- Sw1(config-mst)# revision <#>
- Sw1(config-mst)# name <name></name>
- Sw1(config-mst)# instance <#> vlan <vlan-list></vlan-list>
What is the main different between *R/PVST+* and *MST*?
With PVST and RPVST, there is an instance of STP running per VLAN. With MST, there is one instance of STP running per “bundle” of VLANs.
What is an *MSTI*?
An MSTI is a MST Instance where one or more VLANs are bundled. Maximum of 16 instances supported, and by default, all VLANs are mapped to Instance-0. Each MSTI represents a different STP topology.
What are the compatible parameters required for bridges in *MST*?
The compatible parameters are…
- MST Region Name
- MST Revision Number (static)
- VLAN-to-Instance Mapping Configuration Digest
How would you create a separate STP Topology in *MST*?
To create separate STP Topologies, you would need to tweak STP variables per instance.
What is the *MST BPDU* composed of?
MST BPDU always contains Instance-0 information, and an mrecord of any other instances that would apply across that link.
Why is Instance-0 in MST important?
Instance-0 in MST has all the timer information, and is also used to negotiate with non-MST instances.
What is an *MST Boundary Port*?
An MST Boundary Port are ports unable to do MST with the peer.
What is an *MST Internal Port*?
An MST internal Port are ports that can communicate using MST BPDUs.
What are the two root bridges in MST?
MST has two root bridges, one is the Main Root Bridge (CST) and the other is the IST Master.
