Mac OSX : Tracing which network interface will be used to route traffic to an IP/DNS address

If you have multiple connections on your device (and maybe you have a zero trust client installed); how do you find out which network interface on your device will be used to route the traffic?

Below is a route get request for googles DNS service:

$ route get 8.8.8.8

   route to: dns.google
destination: dns.google
    gateway: 100.64.0.1
  interface: utun3
      flags: <UP,GATEWAY,HOST,DONE,WASCLONED,IFSCOPE,IFREF>
 recvpipe  sendpipe  ssthresh  rtt,msec    rttvar  hopcount      mtu     expire
       0         0         0         0         0         0      1400         0

If you have multiple interfaces enabled, then the first item in the Service Order will be used. If you want to see the default interface for your device:

$ route -n get 0.0.0.0 | grep interface
  interface: en0

Lets go an see whats going on in my default interface:

$ netstat utun3 | grep ESTABLISHED
tcp4       0      0  100.64.0.1.65271       jnb02s11-in-f4.1.https ESTABLISHED
tcp4       0      0  100.64.0.1.65269       jnb02s02-in-f14..https ESTABLISHED
tcp4       0      0  100.64.0.1.65262       192.0.73.2.https       ESTABLISHED
tcp4       0      0  100.64.0.1.65261       192.0.73.2.https       ESTABLISHED
tcp4       0      0  100.64.0.1.65260       192.0.73.2.https       ESTABLISHED
tcp4       0      0  100.64.0.1.65259       192.0.73.2.https       ESTABLISHED
tcp4       0      0  100.64.0.1.65258       192.0.73.2.https       ESTABLISHED
tcp4       0      0  100.64.0.1.65257       192.0.73.2.https       ESTABLISHED
tcp4       0      0  100.64.0.1.65256       192.0.73.2.https       ESTABLISHED
tcp4       0      0  100.64.0.1.65255       192.0.73.2.https       ESTABLISHED
tcp4       0      0  100.64.0.1.65254       192.0.78.23.https      ESTABLISHED
tcp4       0      0  100.64.0.1.65253       192.0.76.3.https       ESTABLISHED
tcp4       0      0  100.64.0.1.65252       192.0.78.23.https      ESTABLISHED
tcp4       0      0  100.64.0.1.65251       192.0.76.3.https       ESTABLISHED
tcp4       0      0  100.64.0.1.65250       192.0.78.23.https      ESTABLISHED
tcp4       0      0  100.64.0.1.65249       192.0.76.3.https       ESTABLISHED
tcp4       0      0  100.64.0.1.65248       ec2-13-244-140-3.https ESTABLISHED
tcp4       0      0  100.64.0.1.65247       192.0.73.2.https       ESTABLISHED