Brocade FastIron Ethernet Switch Platform and Layer 2 Switching Configuration Guide - Manual (Page 79)

MRP uses Ring Health Packets (RHPs) to monitor the health of the ring. An RHP is an MRP protocol
packet. The source address is the MAC address of the master node and the destination MAC address
is a protocol address for MRP. The Master node generates RHPs and sends them on the ring. The
state of a ring port depends on the RHPs.
RHP processing in MRP Phase 1
A ring interface can have one of the following MRP states:
• Preforwarding (PF) - The interface can forward RHPS but cannot forward data. All ring ports begin in
this state when you enable MRP.
• Forwarding (F) - The interface can forward data as well as RHPs. An interface changes from
Preforwarding to Forwarding when the port preforwarding time expires. This occurs if the port does
not receive an RHP from the Master, or if the forwarding bit in the RHPs received by the port is off.
This indicates a break in the ring. The port heals the ring by changing its state to Forwarding. The
preforwarding time is the number of milliseconds the port will remain in the Preforwarding state
before changing to the Forwarding state, even without receiving an RHP.
• Blocking (B) - The interface cannot forward data. Only the secondary interface on the Master node
can be Blocking.
When MRP is enabled, all ports begin in the Preforwarding state. The primary interface on the Master
node, although it is in the Preforwarding state like the other ports, immediately sends an RHP onto the
ring. The secondary port on the Master node listens for the RHP.
• If the secondary port receives the RHP, all links in the ring are up and the port changes its state to
Blocking. The primary port then sends another MRP with its forwarding bit set on. As each of the
member ports receives the RHP, the ports changes their state to Forwarding. Typically, this occurs in
sub-second time. The ring very quickly enters the fully initialized state.
• If the secondary port does not receive the RHP by the time the preforwarding time expires, a break
has occurred in the ring. The port changes its state to Forwarding. The member ports also change
their states from Preforwarding to Forwarding as their preforwarding timers expire. The ring is not
intact, but data can still travel among the nodes using the links that are up.
The following figure shows an example.
RHP processing in MRP Phase 1
FastIron Ethernet Switch Platform and Layer 2 Switching Configuration Guide 79
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