Force10 Resilient Ring Protocol | 337If the Master node does not receive the Ring Health Frame (RHF) before the fail-period timer expires (aconfigurable timer), the Master node moves from the Normal state to the Ring-Fault state and unblocks itsSecondary port. The Master node also clears its forwarding table and sends a control frame to all othernodes, instructing them to also clear their forwarding tables. Immediately after clearing its forwardingtable, each node starts learning the new topology.Ring FailureIf a Transit node detects a link down on any of its ports on the FRRP ring, it immediately sends alink-down control frame on the Control VLAN to the Master node. When the Master node receives thiscontrol frame, the Master node moves from the Normal state to the Ring-Fault state and unblocks itsSecondary 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 nodebegins learning the new topology.Ring RestorationThe Master node continues sending Ring Health Frames out its primary port even when operating in theRing-Fault state. Once the ring is restored, the next status check frame is received on the Master node'sSecondary port. This will cause the Master node to transition back to the Normal state. The Master nodethen logically blocks non-control frames on the Secondary port, clears its own forwarding table, and sendsa control frame to the Transit nodes, instructing them to clear their forwarding tables and re-learn thetopology.During the time between the Transit node detecting that its link is restored and the Master node detectingthat the ring is restored, the Master node’s Secondary port is still forwarding traffic. This can create atemporary loop in the topology. To prevent this, the Transit node places all the ring ports transiting thenewly restored port into a temporary blocked state. The Transit node remembers which port has beentemporarily blocked and places it into a pre- forwarding state. When the Transit node in the pre-forwardingstate receives the control frame instructing it to clear its routing table, it does so and unblocks thepreviously blocked ring ports on the newly restored port. Then the Transit node returns to the Normal state.Multiple FRRP RingsUp to 255 rings allowed per system. However, it is not recommended on the S-Series to have more than 34rings on the same interface (either a physical interface or a portchannel). More than the recommendednumber of rings may cause interface instability. Multiple rings can be configured with a single switchconnection; a single ring can have multiple FRRP groups; multiple rings can be connected with a commonlink.Member VLAN Spanning Two Rings Connected by One SwitchA Member VLAN can span two rings interconnected by a common switch, in a figure-eight style topology.A switch can act as a Master node for one FRRP Group and a Transit for another FRRP group, or it can bea Transit node for both rings.
