Bridge Identifiers; Mac Address Allocation; Mac Address Reduction; Using Pvst - Cisco WS-C4003 - Catalyst 4000 Chassis Switch Software Configuration Manual

Chapter 7 Configuring Spanning Tree
MISTP-PVST+ conforms to the limits of PVST+; for example, you can only configure the amount of
VLAN ports on your MISTP-PVST+ switches that you configure on your PVST+ switches.

Bridge Identifiers

This section explains how MAC addresses are used in PVST+ and MISTP as unique bridge identifiers:
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MAC Address Allocation

Catalyst 4000 family switches have a pool of 1024 MAC addresses that can be used as bridge identifiers
for VLANs running under PVST+ or for MISTP instances. You can use the show module command to
view the MAC address range.
MAC addresses are allocated sequentially, with the first MAC address in the range assigned to VLAN 1,
the second in the range assigned to VLAN 2, and so forth. The last MAC address in the range is assigned
to the supervisor engine in-band (sc0) management interface.
For example, if the MAC address range for the supervisor engine is 00-e0-1e-9b-2e-00 to
00-e0-1e-9b-31-ff, the VLAN 1 bridge ID is 00-e0-1e-9b-2e-00, the VLAN 2 bridge ID is
00-e0-1e-9b-2e-01, the VLAN 3 bridge ID is 00-e0-1e-9b-2e-02, and so forth. The in-band (sc0)
interface MAC address is 00-e0-1e-9b-31-ff.

MAC Address Reduction

The MAC address reduction feature is used on Catalyst 6000 family switches to enable extended-range
VLAN identification. If you have a Catalyst 6000 switch in your network and you have MAC address
reduction enabled on it, you should also enable MAC address reduction on all your Catalyst 4000 family
switches to avoid problems in the spanning tree topology. When MAC address reduction is enabled on
Catalyst 4000 family switches, it disables the pool of MAC addresses used for the VLAN spanning tree,
leaving a single MAC address that identifies the switch. For detailed information on the MAC address
reduction feature, refer to the Catalyst 6000 Software Configuration Guide.

Using PVST+

PVST+ is the default spanning tree mode for Catalyst 4000 family switches. These sections describe
how to configure PVST+ on Ethernet VLANs:
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78-12647-02
MAC Address Allocation, page 7-12
MAC Address Reduction, page 7-12
Default PVST+ Configuration, page 7-13
Configuring PVST+ Bridge ID Priority, page 7-13
Configuring PVST+ Port Cost, page 7-15
Configuring PVST+ Port Priority, page 7-15
Configuring PVST+ Default Port Cost Mode, page 7-16
Configuring PVST+ Port VLAN Cost, page 7-16
Software Configuration Guide—Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4
Bridge Identifiers
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