User Manual

M4300 Intelligent Edge Series Fully Managed Stackable Switches
Configuration Examples User Manual710
and only one MSTI or CIST). For example, port A can be forwarding for instance 1 while
discarding for instance 2. The port states changed since IEEE 802.1D specification.
To support multiple spanning trees, a MSTP bridge must be configured with an unambiguous
assignment of VLAN IDs (VIDs) to spanning trees. This is achieved by:
1. Ensuring that the allocation of VIDs to FIDs is unambiguous.
2. Ensuring that each FID supported by the Bridge is allocated to exactly one Spanning
Tree
Instance.
The combination of VID to FID and then FID to MSTI allocation defines a mapping of VIDs to
spanning tree instances, represented by the MST Configuration
Table.
With this allocation we ensure that every VLAN is assigned to one and only one MSTI. The
CIST is also an instance of spanning tree with a MSTID of 0.
An instance might occur that has no VIDs allocated to it, but every VLAN must be allocated to
one of the other instances of spanning tree.
The portion of the active topology of the network that connects any two bridges in the same
MST Region traverses only MST bridges and LANs in that region, and never Bridges of any
kind outside the Region, in other words connectivity within the region is independent of
external connectivity
.
MSTP Example Configuration
This example shows how to create an MSTP instance on the switch. The example network
includes three different switches that serve different locations in the network. In this example,
ports 1/0/1-1/0/5 are connected to host stations, so those links are not subject to network
loops. Ports 1/0/6–1/0/8 are connected across switches 1, 2 and 3.
Figure 2. MSTP sample configuration