ifd and  ifl are referenced in log and show commands. This article briefly explains the meaning of these acronyms and shows how ifd and ifl are mapped to an interface when you are looking to gather more information.

• What do the acronyms ifd , ifl , iff , ifa , and iif stand for?

• How can I get more information on the reference to ifd and ifl when analyzing logs or viewing show commands? 

  For example, ifl:85 is displayed in this log:
  Nov 24 20:58:34 2015 hostname master Failed to send the packet (discard), ifl:85 , to SFI.

What these acronyms mean

Here's a brief description of the interface acronyms:

ifd is the physical interface device, whereas ifl is the logical interface, which is usually called a unit. Logical interfaces are always related to a physical interface.

For example, interface ge-1/2/3 would be a physical interface, whereas ge-1/2/3.0 would be a logical unit.

The organization hierarchy continues down with address families ( iff ) as [... family inet] and addresses ( ifa ) as [... address 10.1.2.3/24] .

interfaces {
     ge-1/2/3 {    /* ifd */
          unit 0 { /* ifl */
               family inet { /* iff */
                    address 10.1.2.3/24 { /* ifa */
                         primary;
                    } 
               } 
          } 
     } 

}

Mapping the acronyms to an interface:

To identify which interface is referenced in a log message or show command output, use the following hidden commands:

> show interfaces ifl-index <index>
> show interfaces ifd-index <index>

For example, if the log references ifd:1, then run the command:

If the log references ifl:3, then run the command:

Note that it is also possible to obtain the index numbers with this command:

> show interfaces extensive | match "interface|index"| except "stat|flag|descript|speed"
Physical interface: ge-3/1/0, Enabled, Physical link is Up
  Interface index: 138, SNMP ifIndex: 8119, Generation: 141

2026-01-08: Minor, non-technical edits

2019-10-02: Minor, non-technical edits.

• Logical Interface Properties