Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 1485)

EPSR Introduction and Configuration
Software Reference for x310 Series Switches
C613-50046-01 REV A AlliedWare Plus TM Operating System - Version 5.4.4C 57.3
EPSR instances
and domains
Each physical EPSR ring contains one or more EPSR domains. An EPSR instance can be
thought of as a component of an EPSR ring domain that exists on a single node. A set of
instances across the whole ring is called a “domain.” Therefore a ring whose individual
nodes each have two instances results in a two domain ring. Each instance contains a
control VLAN and a number of data VLANs.
The EPSR control VLAN and its associated data VLANs form a Ring Domain. Although a
physical ring can have more than one domain, each domain must operate as a separate
logical group of VLANs and must have its own master node. This means that several
domains may share the same physical network, but must operate as logically separate
VLAN groups.
Control VLAN The function of the control VLAN is to monitor the ring domain and maintain its
operational functions. To do this it transmits and monitors operational healthcheck
messages using EPSR healthcheck control frames. The control VLAN carries no user data.
Data VLAN The data VLAN carries the user data around the ring. Several data VLANs can share a
common control VLAN.
Master node The master node controls the ring operation. It issues healthcheck messages at regular
intervals from its primary port and monitors their arrival back at its secondary port - after
they have circled the ring. Under normal operating conditions the master node’s
secondary port is always in the blocking state to all data VLAN traffic. This is to prevent
data loops forming within the ring. This port however, operates in the forwarding state for
the traffic on the control VLAN. Loops do not occur on the control VLAN because the
control messages stop at the secondary port, having completed their path around the
ring.
Transit nodes The transit nodes operate as conventional Ethernet bridges, but with the additional
capability of running the EPSR protocol. This protocol requires the transit nodes to
forward the healthcheck messages from the master node, and respond appropriately
when a ring fault is detected. The fault condition procedure is explained in
“Fault
Detection and Recovery” on page 57.4 .
Note x310 Series switches within an EPSRing can only operate as Transit Nodes. To
form an EPSR ring using x310 Series switches, you will need to use an
alternative Allied Telesis switch, such as an x610 Series switch or an x510 Series
switch with a Premium License, as the master node.
In the configuration examples shown later in this chapter, master node
configuration is included for completeness; however, the commands shown
will need to be applied to the switch selected to be the master node.