Cisco WS-C2960-24TC-L Software Guide - Page 126
Using MISTP-PVST+ or MISTP, Default MISTP Mode Configuration
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Using MISTP-PVST+ or MISTP Chapter 7 Configuring Spanning Tree Using MISTP-PVST+ or MISTP The default spanning tree mode on the Catalyst 4500 series switches is PVST+ mode. If you want to use MISTP mode in your network, we recommend that you carefully follow the procedures that are described in the following sections in order to avoid loss of connectivity in your network. When you change the spanning tree mode from one mode to another, the current mode stops, the information collected at run-time is used to build the port database for the new mode, and the new spanning tree mode restarts the computation of the active topology. Information about the port states is lost; however, all of the configuration parameters are preserved for the previous mode. If you return to the previous mode, the configuration will still be there. Note We recommend that if you wish to use MISTP mode, you should configure all of your Catalyst 4500 series switches to run MISTP. To use MISTP mode, you first enable an MISTP instance, and then map at least one VLAN to the instance. You must have at least one forwarding port in the VLAN in order for the MISTP instance to be active. If you are changing a switch from PVST+ mode to MISTP mode and you have other switches in the network that are using PVST+, you must first enable MISTP-PVST+ mode on each switch on which you intend to use MISTP so that PVST+ BPDUs can flow through the switches while you configure them. When all switches in the network are configured in MISTP-PVST+, you can then enable MISTP on all of the switches. Default MISTP Mode Configuration Table 7-5 shows the default configuration for MISTP and MISTP-PVST+ modes. Table 7-5 MISTP Mode Default Configuration Feature Enable state MAC address reduction Bridge priority Bridge ID priority Port priority Port cost Default port cost mode Port VLAN priority Port VLAN cost Maximum aging time Default Value Disabled until a VLAN is mapped to an MISTP instance Disabled 32,768 32,769 (bridge priority plus the system ID extension of MISTP instance 1) 32 (global) • Gigabit Ethernet: 4 • Fast Ethernet: 10 • FDDI/CDDI: 10 • Ethernet: 100 Short (802.1D) Same as port priority but configurable on a per-VLAN basis in PVST+ Same as port cost but configurable on a per-VLAN basis in PVST+ 20 sec 7-30 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 78-15486-01
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