Is there any impact on bandwidth when choosing fast (1s) LACPDU timing rather than slow (30s)?
Anyone ever bothered to measure?

I've always assumed it's negligable, with the simple act of bonding probably adding more overhead than any LACPDUs

2 Answers 2


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.

  • Fantastic thanks. Slow mode at 30s does seem largely pointless these days.
    – batfastad
    Commented May 7, 2015 at 10:01

For ISSU on Cisco NX-OS to work you need run LACP configured as "SLOW" and you still detect any issues with the port-channel!

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