Configuring network management-specific
About the network management-specific interface index
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 formats:
16-bit NM-specific ifindex—A 16-bit NM-specific ifindex value contains 16 bits and ranges from 1
to 65534. The NM-specific ifindex value of each interface is allocated dynamically and increased
sequentially. The 16-bit NM-specific ifindex is an index value without any syntax explanation, and
only uniquely identifies an interface.
32-bit NM-specific ifindex—A 32-bit NM-specific ifindex value contains 32 bits, as shown in
33. The value is composed of the following parts: Chassis ID, Slot ID, interface type, and interface
Figure 33 32-bit NM-specific ifindex
Offset—This field is 16 bits in length and distinguishes different interfaces of the same type on the
same interface board.
Interface type—This field is 7 bits in length and is the enumerated value corresponding to the
interface type. It supports up to 128 different interface types and supports more than 80 interface
Slot ID—Number of the physical slot in which the interface resides, with the length of 5 bits.
Chassis ID—This field is 4 bits in length. For a distributed IRF fabric, this field indicates the member
ID of the device to which the interface belongs. For other devices, this field has no meanings and
the value is 0.
Switching the format of an NM-specific ifindex
An NM-specific ifindex adopts the default format (16-bit format). When either of the following scenarios
appears, you need to switch the format of the NM-specific ifindex using the following guidelines:
If the NMS requires a 32-bit NM-specific ifindex, switch the format of the NM-specific ifindex to
32-bit format, which carries interface information, such as the number of the slot in which the
interface resides. If the NMS only supports 16-bit NM-specific ifindex values, the NMS cannot
recognize 32-bit NM-specific ifindex values. Make sure that the NM-specific ifindex values on the
device are 16-bit.
If the network protocol operating on the device does not support 32-bit NM-specific ifindex values,
make sure that NM-specific ifindex values on the device are 16-bit. For example, each packet of
NetStream version 5 or version 8 only reserves 16 bits for the ifindex, and the NM-specific ifindexes
must be in the 16-bit format. Each packet of NetStream version 9 reserves 32 bits for the ifindex, and
the NM-specific ifindexes can be in either 16-bit format or 32-bit format.
Follow these steps to switch the format of an NM-specific ifindex: