Dell PowerConnect B-RX BigIron RX Series Configuration Guide v02.7.03 - Page 479

Ring initialization for shared interfaces 14 node, the packet is forwarded through the secondary interface since it is currently in a preforwarding state. A secondary interface in preforwarding mode ignores any RHP packet that is not from its ring. The secondary interface changes to blocking mode only when the RHP packet forwarded by its primary interface is returned. The packet then continues around Ring 1, through the interfaces on S1 to Ring 2 until it reaches Ring 2's master node. Port 3/2, the secondary interface on Ring 2 changes to blocking mode since it received its own packet, then blocks the packet to prevent a loop. NOTE On the ring member node, the primary and secondary interface is not only decided by the configuration, but also decide by the RHP flow from the ring master. The primary and secondary interface may not be swapped even if the configuration changes and there is an active ring master in the topology. If there is no active ring master in the topology, then the running configuration of the interface on the member node will follow what was configured. Selection of master node Allowing MRP rings to share interfaces limits the nodes that can be designated as the master node. Any node on an MRP ring that does not have a shared interface can be designated as the ring's master node. However, if all nodes on the ring have shared interfaces, nodes that do not have tunnel ports can be designated as the master node of that ring. If none of the nodes meet these criteria, you must change the rings' priorities by reconfiguring the rings' ID. In Figure 72, any of the nodes on Ring 1, even S1 or S2, can be a master node since none of its interfaces are tunnel ports. However in Ring 2, neither S1 nor S2 can be a master node since these nodes contain tunnel ports. RHP processing in rings with shared interfaces Interfaces on an MRP ring have one of the following states: • Preforwarding (PF) - All ring interfaces are in this state when you enable MRP. • Forwarding (F) - An interface changes from Preforwarding to Forwarding when the port's preforwarding time expires. • Blocking (B) - The interface cannot forward data. Only the secondary interface on the Master node can be Blocking. The primary interface of the master node initiates the RHP packets and sends it on the ring. When the packet reaches an interface, MRP checks to see if the receiving interface is a regular port or a tunnel port. If the port is a regular port, the RHP packet is forwarded to the next interface. Forwarding of the packet continues on the ring until the secondary interface of the master node receives the packet and blocks it. If the port is a tunnel port, MRP checks the priority of the RHP packet and compares it to the priority of the tunnel port: • If the RHP packet's priority is less than or equal to the interface's priority, the packet is forwarded through that interface. • If the priority of the RHP packet is greater than the priority of the interface, the RHP packet is dropped. BigIron RX Series Configuration Guide 407 53-1001986-01