Cisco Catalyst 4500 Series Configuration Manual page 1081

Chapter 2
spanning-tree bridge assurance
To enable Bridge Assurance on your network, use the spanning-tree bridge assurance command. To
disable the feature, use the no form of the command.
Syntax Description
This command has no arguments or keywords.
Command Default Bridge Assurance is enabled
Command Modes Global configuration mode
Command History Release
3.8.0E and 15.2.(4)E
Usage Guidelines This feature protects your network from bridging loops. It monitors the receipt of BPDUs on
point-to-point links on all network ports. When a port does not receive BPDUs within the alloted hello
time period, the port is put into a blocked state (the same as a port inconsistent state, which stops
forwarding of frames). When the port resumes receipt of BPDUs, the port resumes normal spanning tree
operations.
By default, Bridge Assurance is enabled on all operational network ports, including alternate and backup
ports. If you have configured the spanning-tree portfast network command on all the required ports
that are connected Layer 2 switches or bridges, Bridge Assurance is automatically effective on all those
network ports.
Only Rapid PVST+ and MST spanning tree protocols support Bridge Assurance. PVST+ does not
support Bridge Assurance.
For Bridge Assurance to work properly, it must be supported and configured on both ends of a
point-to-point link. If the device on one side of the link has Bridge Assurance enabled and the device on
the other side does not, then the connecting port is blocked (a Bridge Assurance inconsistent state). We
recommend that you enable Bridge Assurance throughout your network.
To enable Bridge Assurance on a port, BPDU filtering and BPDU Guard must be disabled.
You can enable Bridge Assurance in conjunction with Loop Guard.
You can enable Bridge Assurance in conjunction with Root Guard. The latter is designed to provide a
way to enforce the root bridge placement in the network.
Disabling Bridge Assurance causes all configured network ports to behave as normal spanning tree ports.
Use the show spanning-tree summary command to see if the feature is enabled on a port.
spanning-tree bridge assurance
no spanning-tree bridge assurance
Modification
Support for the command was introduced.
Catalyst 4500 Series Switch Cisco IOS Command Reference—Release XE 3.9.xE and 15.2(5)Ex
spanning-tree bridge assurance
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