There is one routing table but it can have multiple default gateways: fenrir:~ $ uname -a Darwin fenrir 18.7.0 Darwin Kernel Version 18.7.0: Tue Aug 20 16

There is one routing table but it can have multiple default gateways: fenrir:~ $ uname -a Darwin fenrir 18.7.0 Darwin Kernel Version 18.7.0: Tue Aug 20 16:57:14 PDT 2019; root:xnu-4903.271.2~2/RELEASE_X86_64 x86_64 fenrir:~ $ netstat -rn |head Routing tables Internet: Destination Gateway Flags Refs Use Netif Expire default 172.16.22.254 UGSc 85 732 en0 default 192.168.88.1 UGScI 2 49 en2 127 127.0.0.1 UCS 0 0 lo0 127.0.0.1 127.0.0.1 UH 1 3806 lo0 169.254 link#6 UCS 2 0 en0 ! 169.254 link#8 UCSI 0 0 en2 ! If you bind to a specific interface it will use that default gateway: fenrir:~ $ traceroute -ni en0 google.com traceroute to google.com (216.58.194.142), 64 hops max, 52 byte packets 1 172.16.22.254 0.565 ms 0.340 ms 0.300 ms 2 172.16.25.60 0.893 ms 0.727 ms 0.721 ms 3 172.16.25.0 0.954 ms 0.819 ms 0.815 ms 4 108.218.244.1 7.422 ms 1.908 ms 3.617 ms 5 *^C fenrir:~ $ traceroute -ni en2 google.com traceroute to google.com (216.58.194.142), 64 hops max, 52 byte packets 1 192.168.88.1 12.399 ms 3.768 ms 0.811 ms 2 192.168.80.1 1.950 ms 8.322 ms 1.702 ms 3 172.26.96.161 30.448 ms 393.449 ms 46.537 ms 4 107.72.199.60 182.826 ms 107.72.199.36 34.835 ms 107.72.199.60 50.557 ms 5 12.83.186.101 52.178 ms 32.536 ms 33.431 ms 6 12.83.186.85 38.516 ms 51.138 ms 61.687 ms 7 12.122.5.190 48.626 ms 251.733 ms 38.487 ms 8 12.122.2.197 58.184 ms 82.183 ms^C You can also also do this do this by IP address fenrir:~ $ traceroute -ns 192.168.88.243 google.com traceroute to google.com (216.58.194.142) from 192.168.88.243, 64 hops max, 52 byte packets 1 192.168.88.1 4.658 ms 10.498 ms 3.633 ms 2 192.168.80.1 4.264 ms 58.660 ms 7.153 ms 3 172.26.96.161 105.557 ms 41.207 ms 32.243 ms 4 107.72.199.60 66.562 ms Which interface is used when IP address / interface is not specified is selected by the Service Order setting in the Network control panel.