Honored Contributor.
Honored Contributor.

Lower Layer Down

I have a bunch of Interfaces in a Critical Status and the operational status is "Lower Layer Down" Can someone tell me what this signifies?

1 Reply
Acclaimed Contributor.
Acclaimed Contributor.

Re: Lower Layer Down

Hi John,

  This operational state is defined in RFC 2233 the IF MIB.  Unfortunately is not very expansive it simply states:

                   lowerLayerDown(7) -- down due to state of
                                     -- lower-layer interface(s)

but what it is trying to say is that where there is an interface hierachy e.g. in the past an ISDN interace had two sub interfaces for each of the channels, then if the sub interfaces are "Down" because of line protocol issues or cabling problems, then parent interface is then set to "lowerLayerDown" because it is down due to the sub interfaces being down.   This could also be the case for Aggregated Interfaces if when aggregating them a "parent" interface is created.

  If you review the interfaces in question, can you see if they have sub interfaces?  The structure of their hierachy may be reported in the ENTITY MIB if the agent support this.

  Hope this explains things

Dave Y

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