User's Manual

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the interface.
37.2.8 Configuring Loop Guard
The Loop Guard attribute can protect a port after it changes from a root port or an alternate port to a designated
port. This function can prevent a port from generating a loop when the port cannot receive BPDU continuously.
Root Guard characteristic acts differently somehow in SSTP/PVST and RSTP/MSTP. In SSTP/PVST mode,
designated port is always blocked by Loop Guard. In RSTP/MSTP mode, the port will be blocked when it
changes to designated port if it cannot receive BPDU. An interface receiving low priority BPDU and is of the
designated role will not be blocked by Loopt Guard.
In global configuration mode, run command Loop Guard:
Command Purpose
spanning-tree loopguard default
Globally enables loop guard feature. It is valid to
all interfaces.
no spanning-tree loopguard default
Globally disables loop guard.
Use the following command to configure the Loop Guard feature in the interface configuration mode:
Command Purpose
spanning-tree guard loop
Enables loop guard feature on the interface.
no spanning-tree guard
Disables root guard and loop guard features on
the interface.
spanning-tree guard none
Disables root guard and loop guard features on
the interface.
37.2.9 Configuring Loop Fast
Note:
Please configure this command under the guide of technical engineers.
Loop Fast feature is applied to improve the network convergence in a limited range in special network
environment. For instance, enable Loop Fast feature for all interfaces in the ring network with a dozen of
switches.
Run following commands in global mode to configure Loop Fast feature:
Command Purpose
spanning-tree loopfast
Globally enables Loop Fast feature. It is valid to
all interfaces.