Motorola RFS Series, Справочное руководство системы

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4-156 Motorola RF Switch System Reference Guide
server where all the AP images reside. User ID is the ID to log in to the SFTP server. Password is the SFTP
password used while logging in. Path gives you the path of the AP image residing in the server.
4.10 Multiple Spanning Tree
Multiple Spanning Tree Protocol (MSTP) provides a VLAN-aware protocol and algorithm to create and
maintain a loop-free network. It allows the configuration of multiple spanning tree instances. This ensures
a loop-free topology for one or more VLANs. It allows the network administrator to provide a different path
for each group of VLANs to better utilize redundancy.
MSTP allows rapid convergence similar to Rapid Spanning Tree Protocol (RSTP). RSPT is an independent
protocol and MSTP does not use RSTP. Since MSTP allows VLANs to be grouped in an instance, each
instance can have its own spanning-tree topology independent of other spanning-tree instances. This
architecture provides multiple forwarding links for data traffic and load balancing, and therefore reduces the
number of spanning-tree instances required to support a large number of VLANs.
Using MSTP, the network can be divided into regions. All switches within a region use the same VLAN to
instance mapping. The entire network runs a spanning tree instance called the
Common Spanning Tree
instance (CST) that interconnects regions as well as legacy (STP and RSTP) bridges. The regions run on a local
instance for each configured MSTP instance.
The network-wide spanning tree for instance 0 is known as the Common Spanning Tree (CST). A spanning
tree for any other instance, which is local to a region, is known as an Internal Spanning Tree (IST). The
Common and Internal Spanning Tree (CIST) (which consists of the CST as well as all ISTs across regions)
interconnects all bridges in the network.
The following definitions describe the STP instances that define an MSTP configuration:
• Common Spanning Tree (CST) – MSTP runs a single spanning tree instance (called the Common Spanning
Tree ) that interconnects all the bridges in a network. This instance treats each region as a single bridge.
In all other ways, it operates exactly like Rapid Spanning Tree (RSTP).
• Common and Internal Spanning Trees (CIST) – CIST contains all of the ISTs and bridges not formally
configured into a region. This instance interoperates with bridges running legacy STP and RSTP
implementations.
• Multiple Spanning Tree Instance (MSTI) – The MSTI is identified by an MSTP identifier (MSTPid) value
from 1 to 15. This defines an individual instance of a spanning tree. One or more VLANs can be assigned
to an MSTI. A VLAN cannot be assigned to multiple MSTIs. The multiple spanning tree instance 0 is
always present. VLANs not explicitly assigned to an instance are assigned to instance 0.
• MSTP Region – These are clusters of bridges that run multiple instances of the MSTP protocol. Multiple
bridges detect they are in the same region by exchanging their configuration digest (which is dependent
on the VLAN to instance mapping), region name, and revision-level. If you need to have two bridges in
the same region, the two bridges must have identical VLAN to instance mappings, region names, and
revision-levels.
To configure the switch for MSTP support, configure the region name and the revision on each switch being
configured. This region name is unique to each region. Then create one or more instances and assign IDs.
VLANs are then assigned to instances. These instances must be configured on switches that interoperate
with the same VLAN assignments. Port cost, priority, and global parameters can then be configured for
individual ports and instances.
The Multiple Spanning Tree option contains separate tabs for the following activities:
• Configuring a Bridge