An LACP PDU is around 110 bytes, so running them every second isn't likely to even register on an Ethernet link of any speed.
I would recommend running in "fast" mode at all times for rapid detection of faults.
02-19-2016 12:34 AM - edited 03-08-2019 04:38 AM
Hi,
As per best practice I believe on your VPC Peer-Link you should be running LACP for better failure detection etc.
Now as a general rule I always configure "lacp rate fast" when running LACP to help detect issues sooner and removed from the Port-Channel.
Can you confirm if running "lacp rate fast" is a good move on the Peer-Link
Thanks
Luke
02-19-2016 02:33 AM
Yep, you can use fast lacp hello on peer link
02-19-2016 02:44 AM
Hi Luke,
I think you are right. .
"
You can configure the LACP rate fast feature on the LACP ports of a Cisco Nexus 5000 Series switch or a Cisco Nexus 2000 Series Fabric Extender that is connected to a Cisco Nexus 5000 Series switch.
The LACP rate fast feature is used to set the rate (once every second) at which the LACP control packets are sent to an LACP-supported interface. The normal rate at which LACP packets are sent is 30 seconds.
"
I'm only not sure, how it will act when the connection is flapping. I think that 1 second is not an issue.
Below an answer from another forum:
"
An LACP PDU is around 110 bytes, so running them every second isn't likely to even register on an Ethernet link of any speed.
I would recommend running in "fast" mode at all times for rapid detection of faults.
"
Greetz.
Jeroen
02-19-2016 02:53 AM
The difference between slow and fast LACP modes is the delay between sending hello packets. 30 and 1 seconds respectively. In theory fast LACP mode allows way much faster failure detection of a peer device.
My advice would be to use the LACP fast mode for the Peer-Link on short distances because one of the peers might theoretically end up in a state when the interfaces are up, but the traffic is not being processed. In that case you will most possibly have a 1-30sec traffic disruption.
12-05-2018 05:55 AM
I have a customer who configured a port-channel connecting a Core VDC to an OTV VDC, the port-channel will flap at both ends mentioning that the partner is delayed with the LACP PDU.
For the peer-link I have found that it is not recommended using LACP fast rate.
The defect ID is CSCuu91089, please give it a look.
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