Mac OSX Route Table Traffic Redirection Guide

CloudScale SEO — AI Article Summary

What it is	This article explains how to modify Mac's routing table to redirect traffic from specific websites or IP addresses to different network interfaces using command-line tools.
Why it matters	This technique allows you to control which network connection handles traffic for specific services, which is useful for bypassing VPN tunnels, using different internet connections, or troubleshooting network issues.
Key takeaway	You can reroute specific website traffic on Mac by finding the target IP address, adding a custom route with the route command, and testing the change before making it permanent.

This was a hard article to figure out the title for! Put simply, your mac book has a route table and if you want to move a specific IP address or dns from one interface to another, then follow the steps below:

First find the IP address of the website that you want to re-route the traffic for:

$ nslookup web.whatsapp.com
Server:		100.64.0.1
Address:	100.64.0.1#53

Non-authoritative answer:
web.whatsapp.com	canonical name = mmx-ds.cdn.whatsapp.net.
Name:	mmx-ds.cdn.whatsapp.net
Address: 102.132.99.60

We want to re-route traffic the traffic from: 102.132.99.60 to the default interface. So first lets find out which interface this traffic is currently being routed to?

$ route -n get web.whatsapp.com
   route to: 102.132.99.60
destination: 102.132.99.60
    gateway: 100.64.0.1
  interface: utun0
      flags: <UP,GATEWAY,HOST,DONE,WASCLONED,IFSCOPE,IFREF>
 recvpipe  sendpipe  ssthresh  rtt,msec    rttvar  hopcount      mtu     expire
       0         0         0        34        21         0      1400         0

So this is currently going to a tunnelled interface called utun0 on gateway 100.64.0.1.

Ok, so I want to move if off this tunnelled interface. So lets first display the kernel routing table. The -n option forces netstat to print the IP addresses. Without this option, netstat attempts to display the host names.

$ netstat - rn | head -n 5
Active Internet connections
Proto Recv-Q Send-Q  Local Address          Foreign Address        (state)
tcp4       0    126  100.64.0.1.64770       136.226.216.14.https   ESTABLISHED
tcp4       0      0  100.64.0.1.64768       whatsapp-cdn-shv.https ESTABLISHED
tcp4       0      0  100.64.0.1.64766       52.178.17.3.https      ESTABLISHED

Now we want to re-route whatsapp to the default interface. So lets get the IP address of the default interface.

$ netstat -nr | grep default
default            192.168.8.1        UGScg                 en0
default                                 fe80::%utun1                            UGcIg               utun1
default                                 fe80::%utun2                            UGcIg               utun2
default                                 fe80::%utun3                            UGcIg               utun3
default                                 fe80::%utun4                            UGcIg               utun4
default                                 fe80::%utun5                            UGcIg               utun5
default                                 fe80::%utun0                            UGcIg               utun0

We can see that our en0 interface is on IP address: 192.168.8.1. So lets re-route the traffic from Whatsapp’s ip address to this interace’s IP address:

$ sudo route add 102.132.99.60 192.168.0.1
route: writing to routing socket: File exists
add host 102.132.99.60: gateway 192.168.8.1: File exists

Now lets test if we are routing via the correct interface:

$ route -n get 102.132.99.60
   route to: 102.132.99.60
destination: 102.132.99.60
    gateway: 192.168.8.1
  interface: utun6
      flags: <UP,GATEWAY,HOST,DONE,STATIC>
 recvpipe  sendpipe  ssthresh  rtt,msec    rttvar  hopcount      mtu     expire
       0         0         0         0         0         0      1400         0

Finally delete the route and recheck the routing:

$ sudo route delete 102.132.99.60
delete host 102.132.99.60

$ route -n get 102.132.99.60
   route to: 102.132.99.60
destination: 102.132.99.60
    gateway: 100.64.0.1
  interface: utun6
      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

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Mac OSX: Altering the OS route table to re-direct the traffic of a website to a different interface (eg re-routing whatsapp traffic to en0)

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