Using Mistp-Pvst+ Or Mistp; Default Mistp Mode Configuration - Cisco WS-C2948G-GE-TX Configuration Manual

Using MISTP-PVST+ or MISTP

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.
We recommend that if you wish to use MISTP mode, you should configure all of your Catalyst 4500
Note
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 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
Table 7-5
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
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
7-30
shows the default configuration for MISTP and MISTP-PVST+ modes.
MISTP Mode Default Configuration
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 per VLAN in PVST+
Same as port cost but configurable per VLAN in PVST+
20 sec
Chapter 7 Configuring Spanning Tree
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