Allied Telesis SwitchBlade x3100 Series Manual page 465

EPSR and (R)STP Interaction
4.6.14.1 EPSR and STP Interaction
The EPSR and (R)STP topologies conceptually do the same thing: provide a protection scheme for the network
while blocking certain links to prevent loops. The key difference between the two features, however, is that:
• EPSR requires the user to explicitly create the ring configuration and to decide where blocking will occur for
the data VLAN(s).
• (R)STP configures where links are to be broken based on user provisioned values which are calculated to
determine the lowest cost paths for data traffic. This is used to determine which paths allow data traffic and
where links should be blocked to prevent loops.
It is possible to coordinate these features (through the provisioning of key parameters) so that certain devices can
take part in both EPSR and (R)STP. By data filling these parameters correctly, the blocking of links to remove
loops is coordinated.
Note: One key aspect of providing this coordination is that provisioning must ensure that with ports
that are part of both EPSR and (R)STP, their spanning tree states must be controlled by
EPSR. This is explained in more detail later.
The following configurations are supported:
• Connection of an (R)STP subnetwork to a single node in the EPSR ring.
• Connection of an (R)TP subnetwork to two adjacent nodes of the EPSR ring.
Figure 4-17 shows these two configurations.
Software Reference for SwitchBlade x3100 Series Switches (Layer Two Switching)
Introduction
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