3Com 4210G Series Configuration Manual page 736

Single ring
As shown in Figure 3-2, there is only a single ring in the network topology. In this case, you only need
to define an RRPP domain.
Figure 3-2 Schematic diagram for a single-ring network
Tangent rings
As shown in Figure 3-3, there are two or more rings in the network topology and only one common
node between rings. In this case, you need to define an RRPP domain for each ring.
Figure 3-3 Schematic diagram for a tangent-ring network
Intersecting rings
As shown in Figure 3-4, there are two or more rings in the network topology and two common nodes
between rings. In this case, you only need to define an RRPP domain, and configure one ring as the
primary ring and the other rings as subrings.
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