Hi Andy

On Sat, 25 May 2024, 10:22 Andy Smith via BitFolk Users, <users@mailman.bitfolk.com> wrote:

Here's the configuration:

auto bond0
iface bond0 inet static
bond_mode 1
slaves eth0 eth1
bond_miimon 100

You're correct; bond mode 1 doesn't use LACP

But also, as far as I understand, mode 1 (active-backup) doesn't

require any LACP support in the switches so maybe doesn't care about
LACPDU and only uses link state?

This isn't using LACP, so it doesn't benefit from any of the monitoring and control that LACP brings, and is essentially "blind" and as you say relies purely on the link state. If this was configured using mode 4, with fast LACP, then the LACPDUs are exchanged once every second, allowing rapid detection of this and other issues where the interface remains up but doesn't forward traffic. This is far faster than relying on BGP for link detection, and mode 4 is the only configuration I trust for production use, since failover occurs on the order of seconds rather than a minute or more.

Thanks

Maria