Brocade FastIron Ethernet Switch Platform and Layer 2 Switching Configuration Guide - Manual (Page 323)

that there is no better bridge on the network and sets the ports to FORWARDING. This could cause a
Layer 2 loop.
The following configuration is correct.
device(config)#default-vlan-id 1000
device(config)#vlan 1
device(config-vlan-1)#tagged ethernet 1/1 to 1/2
device(config-vlan-1)#exit
device(config)#interface ethernet 1/1
device(config-if-1/1)#pvst-mode
device(config-if-1/1)#dual-mode
device(config-if-1/1)#exit
device(config)#interface ethernet 1/2
device(config-if-1/2)#pvst-mode
device(config-if-1/2)#dual-mode
device(config-if-1/2)#exit
Setting the ports as dual-mode ensures that the untagged IEEE 802.1Q BPDUs reach the VLAN 1
instance.
PVRST compatibility
PVRST, the "rapid" version of per-VLAN spanning tree (PVST), is a Cisco proprietary protocol. PVRST
corresponds to the Brocade full implementation of IEEE 802.1w (RSTP). Likewise, PVST, also a Cisco
proprietary protocol, corresponds to the Brocade implementation of IEEE 802.1D (STP). When a
Brocade device receives PVRST BPDUs on a port configured to run 802.1w, it recognizes and
processes these BPDUs and continues to operate in 802.1w mode.
PVRST compatibility is automatically enabled when a port receives a PVRST BPDU.
BPDU guard
In an STP environment, switches, end stations, and other Layer 2 devices use Bridge Protocol Data
Units (BPDUs) to exchange information that STP will use to determine the best path for data flow.
The BPDU guard, an enhancement to STP, removes a node that reflects BPDUs back in the network. It
enforces the STP domain borders and keeps the active topology predictable by not allowing any
network devices behind a BPDU guard-enabled port to participate in STP.
In some instances, it is unnecessary for a connected device, such as an end station, to initiate or
participate in an STP topology change. In this case, you can enable the STP BPDU guard feature on
the Brocade port to which the end station is connected. STP BPDU guard shuts down the port and puts
it into an errdisable state. This disables the connected device's ability to initiate or participate in an STP
topology. A log message is then generated for a BPDU guard violation, and a CLI message is displayed
to warn the network administrator of a severe invalid configuration. The BPDU guard feature provides a
secure response to invalid configurations because the administrator must manually put the interface
back in service if errdisable recovery is not enabled.
NOTE
BPDU guard is not supported on tagged ports. It can be configured on a tagged port, but the
configuration will have no effect.
PVRST compatibility
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