H3C Technologies H3C S7500E Series Switches - Manual (Page 77)

7-6
In an RRPP domain, a transit node learns the Hello timer value and the Fail timer value on the
master node through the received Hello packets, ensuring that all nodes in the ring network are
consistent in the two timer settings. A transit node, however, cannot learn the Fast-Hello timer
value and the Fast-Fail timer value set on the master node through received Fast-Hello
packets.
How RRPP Works
Polling mechanism
The polling mechanism is used by the master node of an RRPP ring to check the Health state of
the ring network.
The master node sends Hello packets out its primary port periodically, and these Hello packets
travel through each transit node on the ring in turn.
z If the ring is complete, the secondary port of the master node will receive Hello packets
before the Fail timer expires and the master node will keep the secondary port blocked.
z If the ring is torn down, the secondary port of the master node will fail to receive Hello
packets before the Fail timer expires. The master node will release the secondary port from
blocking data VLANs while sending Common-Flush-FDB packets to instruct all transit
nodes to update their own MAC entries and ARP/ND entries.
Link down alarm mechanism
The transit node, the edge node or the assistant-edge node sends Link-Down packets to the
master node immediately when they find any of its own ports belonging to an RRPP domain is
down. Upon the receipt of a Link-Down packet, the master node releases the secondary port
from blocking data VLANs while sending Common-Flush-FDB packet to instruct all the transit
nodes, the edge nodes and the assistant-edge nodes to update their own MAC entries and
ARP/ND entries. After each node updates its own entries, traffic is switched to the normal link.
Ring recovery
The master node may find the ring is restored after a period of time after the ports belonging to
the RRPP domain on the transit nodes, the edge nodes, or the assistant-edge nodes are
brought up again. A temporary loop may arise in the data VLAN during this period. As a result,
broadcast storm occurs.
To prevent temporary loops, non-master nodes block them immediately (and permit only the
packets of the control VLAN to pass through) when they find their ports accessing the ring are
brought up again. The blocked ports are activated only when the nodes are sure that no loop
will be brought forth by these ports.
Broadcast storm suppression mechanism in a multi-homed subring in case of SRPT
failure
As shown in Figure 7-5 , Ring 1 is the primary ring, and Ring 2 and Ring 3 are subrings. When
the two SRPTs between the edge node and the assistant-edge node are down, the master