MST

Question 1

MST

Answer 1

802.1S

Multiple Spanning Tree Protocol

MST is one of the three STP modes supported on Catalyst switches.

MST provides a blended approuch by mapping one or multiple VLAN’s into a single STP tree, called and MST instance (MSTI).

Question 2

MST region

Answer 2

A grouping of MST switches with the same high-level configuration is known as an MST region.

Question 3

MST Instances

Answer 3

MST uses a special STP instance called the internal spanning tree (IST), which is always the first instance, instance 0. The IST runs on all switch port interfaces for switches in the MST region, regardless of the VLAN’s associated with the ports.

Additional information about other MSTI’s is included (nested) in the IST BPDU that is transmitted throughout the MST region. This enables the MST to advertise only one set of BPDU’s, minimizing STP traffic regardless of the number of instances.

Question 4

MST region boundary

Answer 4

Is any port that connects to a switch that is in a different MST region or that connects to 802.1D or 802.1W BPDU’s.