@user_3534491 hello,
actually, BFD could detect the layer 2 link. It's called multicast BFD.
Please refer the command below,
#
bfd t1 bind peer-ip default-ip interface Eth-Trunk1
discriminator local 100
discriminator remote 200
process-interface-status
commit
#
With these configuration, BFD will send detect packets to multicast address(224.0.0.107~224.0.0.250).