Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 508)

478 Multi-Service IronWare Switching Configuration Guide
53-1003036-02
Ring initialization
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A ring interface can have one of the following MRP states:
• Preforwarding (PF) – The interface will forward RHPs and learn MAC addresses but won’t
forward data for the ring. All ring interfaces start in this state when you enable MRP except the
master node. A blocking interface transitions to preforwarding when the preforwarding timer
expires and no RHP’s have been received.
• Forwarding (F) – The interface will forward RHP’s and data for the ring. On member switches an
interface transitions from preforwarding to forwarding when the preforwarding time expires or
the interface receives an RHP with the forwarding bit set. A break in the ring is indicated if the
secondary interface on the master fails to receive an RHP within the preforwarding timer and
the interface transitions from blocking to forwarding to heal the ring.
• Blocking (B) – The interface can process RHPs, but cannot forward data for the ring. Only the
secondary interface on the master node can be blocking.
NOTE
The configured preforwarding time defines the number of milliseconds the interface will remain in
a state before changing to the next state without receiving an RHP.
When MRP is enabled, all interfaces begin in the preforwarding state and the primary interface on
the master node immediately sends an RHP (RHP 1 in
Figure 107 ) onto the ring. The secondary
interface on the master node listens for the RHP:
• If the secondary interface receives the RHP, all links in the ring are up and the interface
changes its state to blocking. The primary interface then sends another RHP (RHP 2 in
Figure 108 ) with its forwarding bit set on. As each of the member interfaces receives the RHP,
the interfaces change their state to forwarding. Typically, this occurs in sub-second time. The
ring very quickly enters the fully initialized state.
• If the secondary interface does not receive the RHP by the time the preforwarding time expires,
a break has occurred in the ring. The secondary interface changes its state to forwarding. The
ring is not intact, but data is still forwarded among the nodes using the links that are up.
Figure 108 shows an example.