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Figure 37. Normal Operating FRRP Topology
A virtual LAN (VLAN) is configured on all node ports in the ring. All ring ports must be members of the Member VLAN and the
Control VLAN.
The Member VLAN is the VLAN used to transmit data as described earlier.
The Control VLAN is used to perform the health checks on the ring. The Control VLAN can always pass through all ports in the
ring, including the secondary port of the Master node.
Ring Status
The ring failure notification and the ring status checks provide two ways to ensure the ring remains up and active in the event of
a switch or port failure.
Ring Checking
At specified intervals, the Master node sends a ring health frame (RHF) through the ring. If the ring is complete, the frame is
received on its secondary port and the Master node resets its fail-period timer and continues normal operation.
If the Master node does not receive the RHF before the fail-period timer expires (a configurable timer), the Master node moves
from the Normal state to the Ring-Fault state and unblocks its Secondary port. The Master node also clears its forwarding table
and sends a control frame to all other nodes, instructing them to also clear their forwarding tables. Immediately after clearing its
forwarding table, each node starts learning the new topology.
Ring Failure
If a Transit node detects a link down on any of its ports on the FRRP ring, it immediately sends a link-down control frame on the
Control VLAN to the Master node.
When the Master node receives this control frame, the Master node moves from the Normal state to the Ring-Fault state
and unblocks its Secondary port. The Master node clears its routing table and sends a control frame to all other ring nodes,
instructing them to clear their routing tables as well. Immediately after clearing its routing table, each node begins learning the
new topology.
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Force10 Resilient Ring Protocol (FRRP)