How Rrpp Works - H3C LS-3100-52P-OVS-H3 Operation Manual

secondary port receives the Hello packets sent by the local master node before the Fail timer
expires, the overall ring is in Health state. Otherwise, the ring transits into Disconnect state.
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.
The Fail timer value must be greater than or equal to three times of the Hello timer value.
In a dual-homed-ring network, to avoid temporary loops when the primary ring fails, ensure that the
difference between the Fail timer value on the master node of the subring and that on the master
node of the primary ring is greater than twice the Hello timer value of the master node of the
subring.

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.
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.
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.
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