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Configuring MSTP Features
Default MSTP Configuration
Table 15-3
Table 15-3
Default MSTP Configuration
Feature
Spanning-tree mode
Switch priority (configurable on a per-CIST port basis)
Spanning-tree port priority (configurable on a per-CIST port basis)
Spanning-tree port cost (configurable on a per-CIST port basis)
Hello time
Forward-delay time
Maximum-aging time
Maximum hop count
For information about the supported number of spanning-tree instances, see the
Spanning-Tree Instances" section on page
MSTP Configuration Guidelines
These are the configuration guidelines for MSTP:
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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
15-12
shows the default MSTP configuration.
MSTP is supported only on NNIs on the switch. UNIs do not participate in MSTP.
When you enable MST by using the spanning-tree mode mst global configuration command, RSTP
is automatically enabled.
For two or more 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 switch supports up to 16 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
14-10. For information on the recommended trunk port configuration, see the
Other Features" section on page
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.
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
Default Setting
Rapid PVST+ (PVST+ and MSTP are disabled).
32768.
128.
1000 Mbps: 4.
100 Mbps: 19.
10 Mbps: 100.
2 seconds.
15 seconds.
20 seconds.
20 hops.
14-10.
11-16.
Chapter 15
Configuring MSTP
"Supported
"Interaction with
78-17058-01
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