Mstp Instance - Avaya 2330 Manual

MSTP instance

With MSTP instances, traffic can be load-balanced between all the links. Within a region, each
instance has its own independent spanning tree. It can have its own root bridge. Each bridge
can have a different priority for each instance, so that the bridge can be selected as root in one
instance and non-root in another instance.
In the following figure, Switch B is root in Instance #1. Switch C is the root bridge in Instance
#2. In CST, Switch A is the root.
Figure 10: Network with multiple instances configured
VLANs can be assigned arbitrarily to any instance. Any VLAN can be part of one and only one
instance. The VLAN traffic inside the MSTP region takes the path determined by the Spanning
Tree associated with that particular instance. For example, if VLANs 2–50 are associated with
Instance #1 and VLANs 51–100 are associated with Instance #2, the VLAN traffic (VLAN ID
2–50) never takes the link AC path until and unless the link AB or BC fails. Similarly, the VLAN
traffic (VLAN ID 51–100) never takes the link AB path until and unless link CB or CA fails.
Configuration — Layer 2 Ethernet
Spanning Tree Protocol
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