Configuring ERP ERP Overview
OmniSwitch AOS Release 7 Network Configuration Guide March 2011 page 9-7
ERP and RRSTP Differences
ERP and the Ring Rapid Spanning Tree Protocol (RRSTP) are both used for the prevention of loops in
ring-based topologies but have the following differences in their implementation and functionality:
• RRSTP uses a different destination MAC address for each ring, based on the ring ID. ERP uses the
same destination MAC address for all ERP protocol frames and identifies the ring based on a unique
Service VLAN associated with each ring, which carries the ERP protocol frames.
• When a link failure is detected, RRSTP quickly sets the blocking ports to a forwarding state but relies
on MSTP for actual protocol convergence. ERP does not require any support from MSTP. ERP has an
inherent mechanism to recover from a failed state once the failed link is active again.
• MSTP determines which ports of a fully active RRSTP ring are blocked. The blocked ports (Ring
Protection Link) for an ERP ring is pre-determined and configured by the user.
• RRSTP requires a ring of contiguous RRSTP nodes. ERP allows non-ERP nodes to participate in the
ring by using the connectivity monitoring capabilities of Ethernet OAM to alert ERP of a link failure
through non-ERP nodes.
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