Hirschmann RS20 Programming Manual page 44

Sub-Ring (RSR20, RSR30, MACH1000)
Note: Sub-Rings use MRP. You can couple Sub-Rings to existing basis rings
with the HIPER-Ring protocol, the Fast HIPER-Ring protocol and MRP.
When you couple a Sub-Ring to a basis ring under MRP, you configure both
rings in different VLANs. You configure
either the Sub-Ring ports of the Sub-Ring Manager and the devices of the
Sub-Ring in a separate VLAN. Here multiple Sub-Rings can use the same
VLAN.
or the devices of the basis ring, including the basis ring ports of the Sub-
Ring Manager, in a separate VLAN. This reduces the configuration work
when you are coupling multiple Sub-Rings to a basis ring.
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Redundanz L2P
Release 5.0 04/09