Cisco 2950 Software Configuration Guide - Page 330
Default MSTP Configuration, MSTP Configuration Guidelines
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Configuring MSTP Features Chapter 15 Configuring MSTP Default MSTP Configuration Table 15-3 shows the default MSTP configuration. Table 15-3 Default MSTP Configuration Feature Spanning-tree mode Switch priority (configurable on a per-CIST interface basis) Spanning-tree port priority (configurable on a per-CIST interface basis) Spanning-tree port cost (configurable on a per-CIST interface basis) Hello time Forward-delay time Maximum-aging time Maximum hop count Default Setting PVST+ (Rapid PVST+ and MSTP are disabled). 32768. 128. 1000 Mbps: 4. 100 Mbps: 19. 10 Mbps: 100. 2 seconds. 15 seconds. 20 seconds. 20 hops. For information about the supported number of spanning-tree instances, see the "Supported Spanning-Tree Instances" section on page 14-9. MSTP Configuration Guidelines These are the configuration guidelines for MSTP: • When you enable MST by using the spanning-tree mode mst global configuration command, RSTP is automatically enabled. Per-VLAN RSTP is not supported in software releases earlier than Cisco IOS Release 12.1(13)EA1. • 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. • 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. • 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 15-12 Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide 78-11380-10
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