RRPPDUs of subrings are transmitted as data packets in the primary ring, while RRPPDUs of the
primary ring can only be transmitted within the primary ring.
When RRPP checks the link state of an Ethernet ring, the master node sends Hello packets out the
primary port according to the Hello timer and determines whether its secondary port receives the Hello
packets based on the Fail timer.
The Hello timer specifies the interval at which the master node sends Hello packets out the primary
The Fail timer specifies the maximum delay between the master node sending Hello packets out
the primary port and the secondary port receiving the Hello packets from the primary port. If the
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.
How RRPP Works
The polling mechanism is used by the master node of an RRPP ring to check the Health state of the ring
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