How Rrpp Works - H3C S7500E Series Operation Manual

Operation Manual – RRPP
H3C S7500E Series Ethernet Switches

1.1.4 How RRPP Works

I. Polling mechanism
The primary port of the master node sends Health packets across the control VLAN
periodically.
If the ring works properly, the secondary port of the master node will receive
Health packets and the master node will maintain it in block state.
If the ring is torn down, the secondary port of the master node will not receive
Health packets after the timeout timer expires. The master node will release the
secondary port from blocking data VLAN while sending Common-Flush-FDB
packets to notify all transit nodes to update their own MAC entries and ARP
entries.
II. 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 port 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 VLAN while sending Common-Flush-FDB packet to
notify all the transit nodes, the edge nodes and the assistant nodes to update their own
MAC entries and ARP entries.
III. 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 node, the edge node or the assistant edge
node are up again. A temporary loop may arise in the data VLAN in this period. As a
result, broadcast storm occurs.
To prevent temporary loops, non-master nodes block them immediately (and permits
only the packets of the control VLAN) when they find their ports accessing the ring are
up again. The blocked ports are activated only when the nodes ensure that no loop will
be brought forth by these ports.
IV. Broadcast storm suppression mechanism in a multi-homed subring in
case of primary ring link failure
As shown in
When two links of the primary ring between the edge node and the assistant edge node
are down, the master nodes of Ring 2 and Ring 3 will open their respective secondary
ports, and thus a loop among B, C, E and F is generated. As a result, broadcast storm
occurs.
In this case, to prevent from generating this loop, the edge node will block the edge port
temporarily. The blocked edge port is activated only when the edge node ensures that
no loop will be brought forth when the edge port is activated.
Figure 1-5, Ring 1 is the primary ring, and Ring 2 and Ring 3 are subrings.
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Chapter 1 RRPP Configuration