Brocade BigIron RX Series Configuration Guide - Manual (Page 497)

BigIron RX Series Configuration Guide 419
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Ring initialization for shared interfaces
14
How ring breaks are detected and healed between
shared interfaces
If the link between shared interfaces breaks, the secondary interface on Ring 1’s master node
changes to a preforwarding state. The RHP packet sent by port 3/1 on Ring 2 is forwarded through
the interfaces on S4, then to S2. The packet is then forwarded through S2 to S3, but not from S2 to
S1 since the link between the two nodes is not available. When the packet reaches Ring 1’s master
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.