This is an OBJECT IDENTIFIER pointing to protocol-specific MIB definitions relevant to whichever routing protocol, per csOrionVPNVRouterIpRouteProto, is responsible for this route entry, defaulting to the null object identifier 0 0 when not applicable. It gives an admin a pointer into further protocol-specific detail for a route rather than duplicating that detail in this table. An admin drilling from a suspicious OSPF-learned route in the virtual router's table would follow this identifier to the matching OSPF-specific table entry.