I was wondering what would happen if all the uplinks to the spines go down on a leaf in a spine-leaf topology. I was happy to see that the access interfaces configured with ESI's went all down after the bfd timer for the overlay BGP expired.
Still, I was wondering if that is the expected behaviour since I couldn't find any related doc, and I would also like to know if there is a way to control it.
The name of the feature is called "core isolation". It is enabled by default. Basically, if there is no BGP session in the core (for family epvn), then LACP is brought down on all LAG interfaces.
There are some scenarios where you want to disable this feature, namely when there are only 2 devices (Juniper calls this 'collapsed spine' because both leaf and spine function is combined into single device) configured with EVPN/VXLAN.