Specifications

178 ExtremeWare XOS 11.0 Concepts Guide
Ethernet Automatic Protection Switching
Fault Detection and Recovery
EAPS fault detection on a ring is based on a single control VLAN per EAPS domain. This EAPS domain
provides protection to one or more data-carrying VLANs called protected VLANs.
The control VLAN is used only to send and receive EAPS messages; the protected VLANs carry the
actual data traffic. As long as the ring is complete, the EAPS master node blocks the protected VLANs
from accessing its secondary port.
NOTE
The control VLAN is not blocked. Messages sent on the control VLAN must be allowed into the switch
for the master node to determine whether the ring is complete.
To avoid loops in the network, the control VLAN must be NOT be configured with an IP address, and
ONLY ring ports may be added to this VLAN.
A master node detects a ring fault in one of three ways:
• Link down message sent by a transit node
• Ring port down event sent by hardware layers
• Polling response
Link Down Message Sent by a Transit Node
When any transit node detects a loss of link connectivity on any of its ring ports, it immediately sends a
“link down” message on the control VLAN using its good link to the master node.
When the master node receives the “link down” message (see Figure 12), it immediately declares a
“failed” state and opens its logically blocked secondary port on all the protected VLANs. Now, traffic
can flow through the master’s secondary port. The master node also flushes its FDB and sends a
message on the control VLAN to all of its associated transit nodes to flush their forwarding databases as
well, so that all of the switches can learn the new paths to Layer 2 endstations on the reconfigured ring
topology.
primary port A port on the master node that is designated the primary port to the ring. The transit
node ignores the primary port distinction as long as the node is configured as a
transit node.
secondary port A port on the master node that is designated the secondary port to the ring. The
transit node ignores the secondary port distinction as long as the node is configured
as a transit node.
control VLAN A VLAN that sends and receives EAPS messages. You must configure one control
VLAN for each EAPS domain.
protected VLAN A VLAN that carries data traffic through an EAPS domain. You must configure one
or more protected VLANs for each EAPS domain. (Also known as data VLAN)
Table 34: EAPS terms (continued)
Term Description