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DES-7200 Configuration Guide Chapter 5 RERP Configuration
5-2
5.1.2 Typical Applications
Figu
re-1
As shown above, the four devices are all core Ethernet devices and form a ring core
network. In such a topology, each device has two and only two interface to be
connected with the ring. This type of ring is called a RERP region, identified uniquely
with an integer. Each RERP region can have several rings. Each RERP region can
have only one Master and one Backup specified. The others are all Transit. Each
device must be specified with the region and configured with the master/backup port.
Master:
The link is a TRUNK connection. The ring has an independent VLAN as the control
VLAN, which is specially used to transmit various control messages defined by the
RERP. The other VLANs are the data VLANs and used for the transmission of
dataflow.
The two ports of the master connected to the ring are called the primary port and
secondary port respectively, whether the primary port sends the Hello message
outside on regular basis.
Loop blocking:
In normal cases, the master device prevents the generation of layer-2 loop in the
whole ring by blocking the secondary port.
Link interruption:
When a link fails in the Ethernet ring (the link between Transit1 and Transit2 is broken,
for example), both Transit1 and Transit2 may recognize this condition in the link, and
advertise a LINK DOWN message via the control VLAN to the master. When the
master receives it, it clears the layer-2 forwarding table information related with its data
VLAN, and sends the FLUSH NOW message to notify all control devices to clear all
data VLAN related layer-2 forwarding information. At the same time, the BLOCK status
turns into the FORWARDING status.