Destination  Gateway            Flags        Refs      Use   Netif Expire
192.168.1.2  a0:21:b7:c1:91:64  UHLWI           0        3     en3

sudo route add -host 192.168.1.2 -link a0:21:b7:c1:91:64

Destination  Gateway            Flags        Refs      Use   Netif Expire
192.168.1.2  a0:21.b7.c1.91.64  UGHS            0        0   utun0

sudo route add -host 192.168.1.2 -interface en3  -link a0:21:b7:c1:91:64

Destination  Gateway            Flags        Refs      Use   Netif Expire
192.168.1.2  10:dd:b1:a0:af:43  UHLS            0        0   en3