Reference Guide

906 | Rapid Spanning Tree Protocol
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Modify Interface Parameters
On interfaces in Layer 2 mode, you can set the port cost and port priority values.
• Port cost is a value that is based on the interface type. The default values are listed in Table 44-2. The
greater the port cost, the less likely the port will be selected to be a forwarding port.
• Port priority influences the likelihood that a port will be selected to be a forwarding port in case that
several ports have the same port cost.
To change the port cost or priority of an interface, use the following commands:
View the current values for interface parameters using the
show spanning-tree rstp command from EXEC
privilege mode. See Figure 44-5.
Configure an EdgePort
The EdgePort feature enables interfaces to begin forwarding traffic approximately 30 seconds sooner. In
this mode an interface forwards frames by default until it receives a BPDU that indicates that it should
behave otherwise; it does not go through the Learning and Listening states. The
bpduguard
shutdown-on-violation
option causes the interface hardware to be shutdown when it receives a BPDU.
When only
bpduguard is implemented, although the interface is placed in an Error Disabled state when
receiving the BPDU, the physical interface remains up and spanning-tree will drop
packets in the hardware
after a BPDU violation. BPDUs are dropped in the software after receiving the BPDU violation. This
feature is the same as PortFast mode in Spanning Tree.
To enable EdgePort on an interface, use the following command:
Task Command Syntax Command Mode
Change the port cost of an interface.
Range: 0 to 65535
Default: see Table 44-2.
spanning-tree rstp cost cost INTERFACE
Change the port priority of an interface.
Range: 0 to 15
Default: 128
spanning-tree rstp priority priority-value INTERFACE
Caution: Configure EdgePort only on links connecting to an end station. EdgePort can cause loops if it is enabled
on an interface connected to a network.
Task Command Syntax Command Mode
Enable EdgePort on an interface.
spanning-tree rstp edge-port
[bpduguard |
shutdown-on-violation
]
INTERFACE