Each VLAN on each network device has a unique 64-bit bridge ID
consisting of a bridge priority value, an extended system ID, and an
STM MAC address allocation.
This section contains these topics:
* Bridge Priority Value
* Extended System ID
* STP MAC Address Allocation
Bridge Priority Value
With Release 12.1(8a)E and later, the bridge priority is a 4-bit value
when the extended system ID is enabled (see Table 11-2). With earlier
releases, the bridge priority is a 16-bit value (see Table 11-1). See
the "Configuring the Bridge Priority of a VLAN" section.
Extended System ID
Releases 12.1(8a)E and later support a 12-bit extended system ID field
as part of the bridge ID (see Table 11-2). Chassis that support only
64 MAC addresses always use the 12-bit extended system ID. On chassis
that support 1024 MAC addresses, you can enable use of the extended
system ID. STP uses the VLAN ID as the extended system ID. See the
"Enabling the Extended System ID" section.
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