ifd and ifl are referenced in log and show commands. This article briefly explains these acronyms and shows how to map them to the interface in question in order 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.

Description:

Here's a brief description of the interface acronyms:

Acronym	Meaning
ifd	Refers to a physical device
ifl	Refers to a logical device
iff	Refers to an address family
ifa	Refers to an address entry
iif	Refers to an incoming interface, either an ifd or an ifl (uses a kernel interface index, not an SNMP index)

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

For example, interface ge-1/2/3 would be a physical interface, while 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:

It is 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

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