Specifications

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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 13 Configuring RSTP and MSTP
Configuring RSTP and MSTP Features
Default RSTP and MSTP Configuration
Table 13-3 shows the default RSTP and MSTP configuration.
RSTP and MSTP Configuration Guidelines
These are the configuration guidelines for RSTP and MSTP:
• The UplinkFast, BackboneFast, and cross-stack UplinkFast features are not supported with the
PVRST and MSTP.
• Per-VLAN RSTP is not supported in software releases earlier than Release 12.1(13)EA1. When you
enable MST by using the spanning-tree mode mst global configuration command, RSTP is
enabled.
• Per-VLAN RSTP is supported in Release 12.1(13)EA1 or later. When you enable PVRST by using
the spanning-tree mode rapid-pvst global configuration command, RSTP is enabled.
• PVST, PVRST, and MSTP are supported, but only one version can be active at any time; all VLANs
run PVST, all VLANs run PVRST, or all VLANs run MSTP.
• 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.
Table 13-3 Default RSTP and MSTP Configuration
Feature Default Setting
Spanning-tree mode PVST (PVRST and MSTP are disabled).
Switch priority (configurable on a per-CIST interface basis) 32768.
Spanning-tree port priority (configurable on a per-CIST interface basis) 128.
Spanning-tree port cost (configurable on a per-CIST interface basis) 1000 Mbps: 4.
100 Mbps: 19.
10 Mbps: 100.
Hello time 2 seconds.
Forward-delay time 15 seconds.
Maximum-aging time 20 seconds.
Maximum hop count 20 hops.