FUJITSU PSWITCH
User’s Guide
72
December/2018
3.1.2.8.6.
Edge Port
The Edge Port feature reduces the STP convergence time by allowing ports that are
connected to end devices (such as a desktop computer, printer, or file server) to
transition to the forwarding state without going through the listening and learning
states.
3.1.2.8.7.
BPDU (Bridge Protocol Data Unit) Guard
The STP BPDU guard allows network administrator to enforce the STP domain
borders and keep the active topology be consistent and predictable. The switches
behind the edge ports that have STP BPDU guard enabled are not able to influence
the overall STP topology. At the reception of BPDUs, the BPDU guard operation
disables the port that is configured with this option and transitions the port into
disable state. This would lead to administrative disable of the port.
3.1.2.8.8.
Loop Guard
The Loop Guard feature is an enhancement of the Multiple Spanning Tree Protocol.
Loop guard protects a network from forwarding loops induced by BPDU packet loss.
The reasons for failing to receive packets are numerous, including heavy traffic,
software problems, incorrect configuration, and unidirectional link failure. It can be
configured to prevent a blocked port from transitioning to the forwarding state
when the port stops receiving BPDUs for some reason (such as a unidirectional link
failure). When a non-designated port no longer receives BPDUs, the spanning-tree
algorithm considers that this link is loop free and begins transitioning the link from
blocking to forwarding. Once in forwarding state, the link may create a loop in the
network.
Enabling loop guard prevents such accidental loops. When a port is no longer
receiving BPDUs and the max age timer expires; the port is moved to a
loop-inconsistent blocking state. In the loop-inconsistent blocking state, traffic is
not forwarded so the port behaves as if it is in the blocking state. The port will
remain in this state until it receives a BPDU. It will then transition through the
normal spanning tree states based on the information in the received BPDU.
Loop Guard should be configured only on non-designated ports. These
include ports in alternate or backup roles. Root ports and designated ports
should not have loop guard enabled so that they can forward traffic
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