Link state replication, also called interface preservation, is an addition to the SONET Automatic Protection Switching (APS) functionality that helps promote redundancy of link PICs used in LSQ configurations, providing MLPPP link redundancy at the port level.
Link state replication provides the ability to add two sets of links, one from the active SONET PIC and the other from the standby SONET PIC, to the same bundle. If the active SONET PIC fails, links from the standby PIC are used without link renegotiation. All the negotiated state is replicated from the active links to the standby links to prevent link renegotiation. For more information about LSQ configurations, see the JUNOS Services Interfaces Configuration Guide.
To configure link state replication, include the preserve-interface statement at the [edit interfaces interface-name sonet-options aps] hierarchy level on the interfaces on both PICs:
APS functionality must be available on the SONET PICs and the interface configurations must be identical on both ends of the link. Any configuration mismatch causes the commit operation to fail.
This feature is supported with SONET APS and the following link PICs:
Link state replication supports MLPPP and PPP over Frame Relay (frame-relay-ppp) encapsulation, and fully supports GRES.