I came across terms like IFL IFD and IFA 's recently when studying some articles related to my project, I dont clearly understand what they are and the difference between them. I know they are related to interfaces within networking devices. I came across these terms when studying article on Juniper network's website.

1 Answer 1


This juniper-nsp email explains them pretty clearly...

We try to avoid the terms "ifd" and "ifl" completely in our docs, but these internal terms have slipped out in a few places. The relationship is fairly simple: "ifd" is the physical interface device, where "ifl" is the logical interface (aka unit). Logical interfaces are arranged as children of a physical interface... As an example, [interfaces so-1/2/3] would be a physical interface and [interfaces so-1/2/3 unit 0] would be a logical unit. The organization hierarchy continues down with address families (iff) as [... family inet] and addresses (ifa) as [... address].

In summary:

  • ifd: A Junos Physical Interface
  • ifl: A Junos Logical Interface (how individual vlans on a physical interface are distinguished)
  • ifa: A Junos interface address
  • 1
    Another term that is used sometimes is IFF for interface family. For example interface ge-0/0/0 unit 0 family inet Mar 25, 2014 at 9:29

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