User's Manual

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Master node: It positively knows whether the ring’s topology is complete, removes loopback, and controls other
switches to update topology information.
Transit node: It only checks the state of the local port of the ring, and notifies the master node of the invalid
link.
The role of each node can be specified by user through configuration. The thing is that each switch in the same
ring can be set to only one kind of node. In figure 1.1, switch S1 is the master node of ring network, while
switches S2, S3 and S4 are transit nodes.
41.2.2 Role of the Ring’s Port
EAPS demands each switch has two ports to connect the ring network. Each port of the ring network also
needs to be specified through configuration and the protocol supports the following kinds of port roles:
Primary port: the primary port can be configured only on the master node. The master node transmits the ring
detection packets through the primary port.
Secondary port: the secondary port can be configured only on the master node. The master node receives the
ring detection packets from the secondary port and judges whether the topology of the ring network is complete.
In complete topology, the master node blocks the data packets on the secondary port, and prevents loopback
from occurring; after a link on the ring network is interrupted, the master node will open the secondary port to
forward the data packets.
Transit port: the transmit port can only be configured on the transit node. Both ports through which the transit
node connects the ring network are all transit ports.
Each port of the ring network can be configured as only one port role after the node's role of the switch and
the control VLAN are configured. As shown in figure 1.1, the port through which master node S1 connects
transit node S4 is a primary port, the port through which S1 connects S2 is a secondary port, and the ports
through which other switches connect the ring network are all transit ports.
Remarks:
To configure the same switch to multiple rings, the switch must connect different rings through
different physical ports.
41.2.3 Control VLAN and Data VLAN
A private control VLAN is used between master node and transit node to transmit protocol packets. This control
VLAN is specified by user through configuration and ring's ports are added also by user to the control VLAN,
which guarantees that the protocol packets can be normally forwarded. In general, each port of the ring network
is in the forwarding state in the control VLAN and the ports which do not belong to the ring network cannot
forward the packets of control VLAN.
Note:
You can specify different control VLANs for each ring on a switch. The control VLAN is only used
to forward the control packets of the ring network, not for L2/L3 communication. For example, if
the VLAN port that corresponds to the control VLAN is established, the IP address of the VLAN
port cannot be pinged through other devices.
The VLANs except the control VLAN are all data VLANs, which are used to transmit the packets of normal
services or the management packets.