The protection success of the OMCR model relies on grouping protected entities (links and nodes) according to the likelihood of their failure within the time frame required for their restoration. For example, the same resource (IOM card or port) on the protecting node can be used to protect multiple entities in the network if their failures do not overlap in time. In other words, if one failure can be repaired before the next one contending for the same resource on the central standby node, the OMCR model serves the purpose.
Because the oversubscribed model does not offer any guarantees, it is possible that the protecting node in some cases runs out of resources and fails to offer protection. In this case, the protecting node generates an SNMP trap identifying the SRRP instance on which subscriber protection has failed. One SNMP trap is raised per SRRP instance in case where at least one subscriber under the corresponding group interface was not instantiated. The trap is cleared either when all subscribers become instantiated or when the SRRP transition into a non-master state.
The number of the subscriber hosts that failed to instantiate, can also be determined using the operational show>redundancy>multi-chassis all command. This command shows the number of subscribers that failed to instantiate along with SRRP instances on which the subscriber host are relaying for successful connectivity.
Pre-emption of already instantiated subscriber hosts in the protecting node by another subscriber hosts is not allowed.