Say we have two swicthes. Switch A and Switch B.

Switch A sends LACPDU's with timeput flag set to 1 (fast).
Switch B sends LACPDU's with timeout flag set to 0 (slow).

By researching came to know that the switch advertises this as that it is expecting the neighbour to honor it.

I want to understand how this works here.

Is it like by some means both of them negotiate which timeout to use ? Like both sides use fast or slow. If yes, based on what do they identify.

Or is it like the sides continue to use their respective speed.

Like Switch A expects that LACPDU comes every 1 second and Switch B sends it. And Switch B expects that LACPDU come every 30s and Switch A sends it.

1 Answer 1


Short vs long timeout expresses preference for LACPDU timeout - it's not negotiated. Each side sends LACPDUs according to its partner's timeout preference.

See 802.1AX Clause 6.4.1:

d) Periodic transmission of LACPDUs occurs if the LACP_Activity control of either the Actor or the Partner is Active LACP. These periodic transmissions will occur at either a slow or fast transmission rate depending upon the expressed LACP_Timeout preference (Long Timeout or Short Timeout) of the Partner System.


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