NETGEAR S3300-28X (GS728TX) 24x1GE - Инструкция по эксплуатации - Страница 351

 Configuration Examples

351

 S3300 Smart Managed Pro Switch

As there are Multiple Instances of Spanning Tree, there is a MSTP state maintained on a 
per-port, per-instance basis (or on a per port per VLAN basis: as any VLAN can be in one 
and only one MSTI or CIST). For example, port A can be forwarding for instance 1 while 
discarding for instance 2. The port states have changed since IEEE 802.1D specification.

To support multiple spanning trees, a MSTP bridge has to 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 can 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.