LACP - is there a link member keepalive mechanism?

[hgans]

Hi,

a real basic question puzzels me now,

until today I thought when using LACP as Etherchannel protocol,

LACP PDU's are sent over EVERY of the member links of the channel as a keepalive mechanism.

I thought if one link is missing these keepalives the port is removed from channel or maybe put in down state.

Now I am not able to find a evidence for this presumption....

Do you know if LACP is really only a channel control protocol negotiating parameters using one of the channel member links and not also functioning together with a keepalive mechanism for member link status?

What, if there is a converter or other components in the path of channel members not passing link loss?

thanks!

Herwig

[cpembleton · Accepted solution]

LACP uses a lacpdu to exchange information including link state.  Any etherchannel configured as mode active will periodically send out lacpdu's.  Depending on the rate (default: slow = 30s, fast=1s) your platform uses will determine how long before LACP will detect a failure and remove link from etherchannel. 

The Nexus stuff you can set to fast which is 1sec.  Only a few platforms have the option to manualy set the rate to fast. 

'Show lacp NUM detail' will show you the current rate.

If your platform can only operate at slow and you need something faster you can utililze udld aggressive and set the interval as low as 1s. 

HTH

Chad