Friday, November 03, 2017

VMware vSphere DVS LACP timers

I have a customer who was planning a migration from Nexus 1000V (N1K) to VMware Distributed Virtual Switch (aka DVS). I assist their network team in testing DVS functionality and all was nice and shiny. However, they had few detailed LACP related questions because they would like to use LACP against Cisco vPC. I would like to highlight two questions for which I did not find any info in official documentation.

Q1: VMware's LACP is sending LACPDUs every 30 seconds. Is there any way how to configure LACPDU frequency to 1 second?

A1: Short answer is yes. It is possible to reconfigure LACPDU from 30 seconds (normal) to 1 second (fast).

Long answer ... Link Aggregation Control Protocol (LACP) allows the exchange of information with regard to the link aggregation between the two members of said aggregation. This information will be packetized in Link Aggregation Control Protocol Data Units (LACDUs). For further detail about LACP timers see blog post "LACP timer and what it means". In short, LACP timers can be set to "rate fast" - 1 second, or "rate normal" - 30 seconds.

The default value for VMware DVS LACP rate is 30 seconds (normal).  There is esxcli command to configure shorter LACP timer (1 second). See the command help bellow.

esxcli network vswitch dvs vmware lacp timeout set
It allows set advanced timeout settings for LACP
set Set long/short timeout for vmnics in one LACP LAG
Cmd options:
-l|--lag-id= The ID of LAG to be configured. (required)
-n|--nic-name= The nic name. If it is set, then only this vmnic in the lag will be configured.
-t|--timeout Set long or short timeout: 1 for short timeout and 0 for a long timeout. (required)
-s|--vds= The name of VDS. (required)

Q2: Do we have a possibility to display LACP settings of established LACP session in particular ESXi host? Something like "show lacp" on Cisco switch?

A2: Yes. There is esxcli command ... esxcli network vswitch dvs vmware lacp status get ... which is equivalent to "show lacp" on Cisco physical switch.

UPDATE 2019-03-26: I have been informed that LACP timers setting do not persist ESXi reboot. I'm trying to get more information internally within VMware about such unexpected behavior.  


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David Pasek said...

To be honest, I do not care. I do not blog for a living but to support VMware and the broader IT community.

I think, in general, it is very difficult to protect publically available content.

Adam Callaghan said...

Hi David,

Excellent post as always!

Did you get any information back regarding the loss of configuration to LACP timers upon reboot?

Was this, or is this still an active issue?

Many thanks


David Pasek said...

The persistence of this configuration was never implemented. There was the reason why. Anyway, as it has never been implemented it is not internally treated as a bug but rather feature request which is managed by Product Manager. If you are active VMware customer, please do escalate this topic through your TAM, SE, AE, etc. and it can get higher priority to be selected for development.