Relating IFD and IFL indexes to interfaces

This article should assist engineers relate IFL or IFD index numbers seen on logs or show commands to the actual interface in question.

Sometimes when analyzing logs or viewing certain show commands, you will notice that ifl or ifd indexes are referenced in such logs. This prexifes might create confusion when reading the logs as engineer might not be familiar with what ifl or ifd really is. This article should assist is providing a guide on how to understand such indexes.

ifd refers to a physical device
ifl refers to a logical device

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

For example interfaces ge-1/2/3 would be a physical interface and 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].


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James Palmer

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