User guide

Overview SuperLoop Prevention (Superring)
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AlliedView NMS Administration Guide (Configuring Network Services)
6.14 SuperLoop Prevention (Superring)
6.14.1 Overview
Prior to release 9.0., if all the following conditions were present, a loop could occur between nodes when the EPSR feature
was working correctly:
• The network had two or more EPSR domains.
• The protected (data) VLAN overlapped two or more EPSR domains.
• The EPSR domains and the overlapping protected VLANs shared a common link.
When there was a common link failure, each ring would block the appropriate interface, but this could lead to a larger loop,
or SuperLoop, being created. Because of this, EPSR rings that had all the attributes listed above were not allowed.
To resolve the SuperLoop issue, the concept of certain ring interfaces having a priority is introduced. This priority is
assigned to the control VLAN on the interface. The value range is 0 to 127. By default, the priority of each of the ring inter-
faces for an EPSR domain is 0 (the lowest priority), and means there is no change in how the interface and protocol works
prior to release 9.0. The higher values, however, are used when there are interconnected EPSR rings in which the SuperLoop
condition needs to be avoided.
When creating this configuration, which is called a SuperRing, the user will therefore specify an EPSR Priority when an
EPS Ring is created. When the user enters a value greater than 0, this indicates the ring is intended to be used with other peer
rings to form a SuperRing. If the user sets the priority to 0, then the ring will behave as an ordinary EPS Ring as described in
6.13.
As with creating regular EPS Rings, the user should first decide on the VLANs and topologies to be used based on iMAP
recommendations.
The following figure shows how the feature would work with two EPSR rings and an interconnected data VLAN over a
common physical link. This configuration will be the result of using the AlliedView NMS SuperLoop feature that makes up
the rest of this Section.
Note that there are several configuration rules that must be followed since there can be multiple ring domains that share one
or more protected VLANs. These rules are described in detail in the iMAP User Guide. By using the AlliedView NMS to
create an EPSR SuperLoop configuration and following a recommended series of steps, the user can ensure that these rules
are automatically followed. Moreover, there are appropriate warning messages when the user should be made aware of
changes that are being made to a configuration.