Rockwell Automation 284E ArmorStart with EtherNet/IP - User Manual - Manual (Page 62)

62 Rockwell Automation Publication 280E-UM001B-EN-P - July 2012
Chapter 3 Introduction to EtherNet/IP and Device Level Ring Technology
Device Level Ring (DLR) Introduction
A DLR protocol defines a set of behaviors, refer to Figure 44. A ring supervisor
keeps packets of information from circulating infinitely around the ring by
blocking one of the ports. A beacon frame constantly is detected on both ring
supervisor ports. If a beacon frame is not detected the supervisor detects the
physical layer issue and reconfigures the network to a linear topology without the
loss of any node communication or data. Once repaired the ring supervisor
reconfigures back to ring mode.
Figure 44 - DLR Protocol
.
As shown in Figure 45, when a physical layer failure is detected the adjacent
nodes to the fault generate a link status message that the ring supervisor
acknowledges. The ring supervisor unblocks the port to allow communication.
The neighboring nodes to the fault identify the fault and reconfigure themselves
to support a linear topology. Now, both the ring supervisor and nodes are
configured to support a linear topology.
IMPORTANT Products with EtherNet/IP embedded switch technology have two ports to connect to
a linear or DLR network in a single subnet.
You cannot use these ports as two Network Interface Cards (NICs) connected to two
different subnets.