Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 454

During the time between the Transit node detecting that its link is restored and the Master node detecting that the ring is restored, the Master node's Secondary port is still forwarding traffic. This can create a temporary loop in the topology. To prevent this, the Transit node places all the ring ports transiting the newly restored port into a temporary blocked state. The Transit node remembers which port has been temporarily blocked and places it into a pre- forwarding state. When the Transit node in the pre-forwarding state receives the control frame instructing it to clear its routing table, it does so and unblocks the previously blocked ring ports on the newly restored port. Then the Transit node returns to the Normal state. Multiple FRRP Rings Up to 255 rings are allowed per system and multiple rings can be run on one system. More than the recommended number of rings may cause interface instability. You can configure multiple rings with a single switch connection; a single ring can have multiple FRRP groups; multiple rings can be connected with a common link. Member VLAN Spanning Two Rings Connected by One Switch A 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 be a Transit node for both rings. In the following example, FRRP 101 is a ring with its own Control VLAN, and FRRP 202 has its own Control VLAN running on another ring. A Member VLAN that spans both rings is added as a Member VLAN to both FRRP groups. Switch R3 has two instances of FRRP running on it: one for each ring. The example topology that follows shows R3 assuming the role of a Transit node for both FRRP 101 and FRRP 202. Important FRRP Points FRRP provides a convergence time that can generally range between 150ms and 1500ms for Layer 2 networks. The Master node originates a high-speed frame that circulates around the ring. This frame, appropriately, sets up or breaks down the ring. • The Master node transmits ring status check frames at specified intervals. • You can run multiple physical rings on the same switch. • One Master node per ring - all other nodes are Transit. • Each node has two member interfaces - primary and secondary. • There is no limit to the number of nodes on a ring. • Master node ring port states - blocking, pre-forwarding, forwarding, and disabled. • Transit node ring port states - blocking, pre-forwarding, forwarding, and disabled. • STP disabled on ring interfaces. • Master node secondary port is in blocking state during Normal operation. • Ring health frames (RHF) • Hello RHF: sent at 500ms (hello interval); Only the Master node transmits and processes these. Force10 Resilient Ring Protocol (FRRP) 454