Mstp Configuration Guidelines - Cisco WS-CBS3032-DEL Software Configuration Manual

Configuring MSTP Features

MSTP Configuration Guidelines

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Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
19-16
When you enable MST by using the spanning-tree mode mst global configuration command, RSTP
is automatically enabled.
For two or more nonstacking-capable switches to be in the same MST region, they must have the
same VLAN-to-instance map, the same configuration revision number, and the same name.
For two or more stacked switches to be in the same MST region, they must have the same
VLAN-to-instance map, the same configuration revision number, and the same name.
The nonstacking-capable switch supports up to 65 MST instances. The number of VLANs that can
be mapped to a particular MST instance is unlimited.
The switch stack supports up to 65 MST instances. The number of VLANs that can be mapped to a
particular MST instance is unlimited.
PVST+, rapid PVST+, and MSTP are supported, but only one version can be active at any time. (For
example, all VLANs run PVST+, all VLANs run rapid PVST+, or all VLANs run MSTP.) For more
information, see the "Spanning-Tree Interoperability and Backward Compatibility" section on
page 18-11. For information on the recommended trunk port configuration, see the
Other Features" section on page
When the switch is in MST mode, it uses the long path-cost calculation method (32 bits) to compute
the path cost values. With the long path-cost calculation method, these path cost values are
supported:
Speed Path Cost Value
10 Mb/s 2,000,000
100 Mb/s 200,000
1 Gb/s 20,000
10 Gb/s 2,000
100 Gb/s 200
All stack members run the same version of spanning tree (all PVST+, rapid PVST+, or MSTP). For
more information, see the "Spanning-Tree Interoperability and Backward Compatibility" section on
page 18-11.
VTP propagation of the MST configuration is not supported. However, you can manually configure
the MST configuration (region name, revision number, and VLAN-to-instance mapping) on each
switch within the MST region by using the command-line interface (CLI) or through the SNMP
support.
For load-balancing across redundant paths in the network to work, all VLAN-to-instance mapping
assignments must match; otherwise, all traffic flows on a single link. You can achieve
load-balancing across a switch stack by manually configuring the path cost.
All MST boundary ports must be forwarding for load-balancing between a PVST+ and an MST
cloud or between a rapid-PVST+ and an MST cloud. For this to occur, the IST master of the MST
cloud should also be the root of the CST. If the MST cloud consists of multiple MST regions, one
of the MST regions must contain the CST root, and all of the other MST regions must have a better
path to the root contained within the MST cloud than a path through the PVST+ or rapid-PVST+
cloud. You might have to manually configure the switches in the clouds.
13-18.
Chapter 19 Configuring MSTP
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