Switching the NM-specific interface index format
A network management (NM)-specific ifindex identifies an interface and is provided by the SNMP managed device to the NMS. A network management-specific ifindex takes one of the following two formats:
16-bit NM-specific ifindex—The system dynamically assigns 16-bit NM-specific ifindex values to uniquely identify its interfaces. The 16-bit NM-specific ifindex value starts from 1 and increments by 1.
32-bit NM-specific ifindex—A 32-bit NM-specific ifindex value comprises an Offset, Interface Type, Slot ID, and Chassis ID, as shown in Figure 26.
Figure 26: 32-bit NM-specific ifindex
Offset—This field is 16 bits long and distinguishes different interfaces of the same type on the same interface card.
Interface type—This field is 7 bits long and contains the enumerated value specific to the interface type. It supports up to 128 different interface types and supports more than 80 interface types at present.
Slot ID—This field is 5 bits long and contains the number of the physical slot that holds the interface.
Chassis ID—This field is 4 bits long. For a distributed device in IRF mode, this field indicates the IRF member ID of the device that provides the interface. For other types of devices, this field takes on 0 and is always ignored.