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I'm a digital nomad and I like to work in cafes and co-working spaces. The problem is that sometimes the network router IP address conflicts with my company's VPN-client IP address. Any and all requests to my company's internal network are routed to 172., and some are then routed to 10. (an internal region)

While working at Panera, after I connected to the wifi, I was unable to access any 10.* websites on my company's internal VPN, because the Panera wifi created the following rule in my Mac's routing tables:

10 link#14 UCS en0 !

After deleting that rule, and adding my own routing table rule, I was able to connect to the internal website:

% sudo route delete -net 10.0.0.0/8 -interface en0  
delete net 10.0.0.0: gateway en0
% sudo route add -net 10.0.0.0/8 -interface utun4 
add net 10.0.0.0: gateway utun4

And this worked fine at Panera. I was able to connect to the 10.* internal websites.

However, I moved to a different co-working space, and I have a different problem. It looks like the router itself is taking up the same IP address that my VPN tunnel uses, and when I start up the VPN software, I lose all internet.

router IP address

That Router IP address happens to be the exact same IP address that all my VPN traffic is supposed to be routing through. For example, when I run "nslookup" on any of my company's internal websites, here's the result

% nslookup example.internal.com
Server:     172.16.0.1
Address:    172.16.0.1#53

Non-authoritative answer:
Name:   example.internal.com
Address: 10.102.120.40

So my question is what can I do on my local computer, whether through routing table rules or other VPN configuration, so that I can still connect to this router, and also the company's VPN?

For reference, the VPN client i'm using is called BIG-IP Edge Client and it's on a Mac M1. Would it be possible for me to carry around my own portable router that my laptop sees as a 192 address, and then connect that router to the public wifi so that it doesn't conflict?

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  • Sorry, networks not under your control and host configurations are explicitly off-topic here, see the help center. You should talk to you company's IT support or need to sort out the routes yourself.
    – Zac67
    Feb 13 at 7:39

1 Answer 1

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That's the unfortunate, and unavoidable, problem of using other people's networks. The former (10/8) issue should be addressed by your VPN client software -- install a /32 route to the router, and VPN gateway, and then two /1 routes to override any default gateway. The VPN server should also be telling the client about specific protected networks. (aka. split-tunnel)

The second scenario is harder to address. Without VRFs / "namespaces", it's hard to isolate things with the same address. VPN client software can deal with an inside and outside address being the same - it knows what interface is which. The issue is the rest of the OS.

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