Brocade Communications Systems RFS6000 System Reference Manual page 249

Error Disable Timeout Select this option to enable an error disable-timeout facility. The error disable-timeout is used to set a timeout value
for ports disabled resulting from a BPDU guard.
The BPDU guard feature shuts down the port on receiving a BPDU on a BPDU-guard enabled port.
ID Format Selector Displays the ID format currently in use.
PortFast Bdpu Filter Select this checkbox to enable BPDU filter for all portFast-enabled ports.The Spanning Tree Protocol sends BPDUs
from all the ports. Enabling the BPDU filter feature ensures PortFast-enabled ports do not transmit or receive any
BPDUs.
PortFast Bdpu Guard Select this checkbox to enable BPDU guard for all portFast-enabled ports.
When the BPDU Guard feature is set for bridge, all portFast-enabled ports of the bridge that have BPDU set to default
shutdown the port on receiving a BPDU. Hence no BPDUs are processed.
Admin Cisco Mode Select this checkbox to enable interoperability with Cisco's version of MSTP, which is incompatible with standard
MSTP.
Operator Cisco Mode Displays whether Cisco's version of MSTP is running. This is not a configurable parameter.
MST Config Digest Displays the Configuration Digest derived from the MSTP Configuration table.
1. Refer to the General Configuration field for the following
CIST Root This displays the CIST (Common and Internal Spanning Tree) root bridge's bridge identifier. The bridge identifier
consists of a priority value followed by the MAC address.The lower the path cost, the greater the likelihood of the
bridge becoming the root.
External Root Cost Displays the root cost of the CIST root.
Regional Root This displays the regional roots MAC address.
CIST Bridge Priority Set the bridge priority for the common instance. The value entered, determines the likelihood this bridge is selected
as the root.
The lower the priority the greater the likelihood of the bridge becoming a root.
CIST Bridge HelloTime Set the CIST Hello Time (in seconds). After the defined interval all bridges in a bridged LAN exchange BPDUs.
The hello time is the time interval (in seconds) the device waits between BPDU transmissions.
A very low value leads to excessive traffic on the network, whereas a higher value delays the detection of a topology
change. This value is used by all instances.
Bridge Hello Time Displays the configured Hello Time. If this is the root bridge, the value is equal to the configured Hello Time.
CIST Bridge Forward Enter the CIST bridge forward delay value received from the root bridge. If this is the root bridge, the value will be
Delay equal to the Configured Forward Delay.
The forward delay value is the maximum time (in seconds) the root device waits before changing states (from a
listening state to a learning state to a forwarding state).
This delay is required, as every device must receive information about topology changes before forwarding frames.
In addition, each port needs time to listen for conflicting information that would make it return to a blocking state;
otherwise, temporary data loops may result.
CIST Bridge Forward Displays the configured forward delay period.
Delay
CIST Bridge Maximum Enter the CIST bridge maximum age received from the root bridge. The max-age is the maximum time (in seconds)
Age for which (if a bridge is the root bridge) a message is considered valid. This prevents the frames from looping
indefinitely. The max-age should be greater than twice the value of hello time plus one, but less than twice the value
of forward delay minus one. The allowable range for max-age is 6-40 seconds. Configure this value sufficiently high,
so a frame generated by root can be propagated to the leaf nodes without exceeding the max age.
Bridge Maximum Age Displays the BPDU maximum age value. If this is the root bridge, the value will be equal to the Configured Max Age.
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