Combine router VPN with Client VPN

Question

I would like to combine my router's default VPN with another one I run on my laptop.

• Here is what I currently have :

• Here is what I would like to have :

Both router (DD-WRT) and laptop use OpenVPN to connect to their servers, and both connections are working. However, when I use both VPN, I get a "smaller" traceroute whereas I should have (at least) 1 more hop. For example, here is the traceroute with the router VPN only (fake IP addresses used here) :

$ traceroute 8.8.8.8
traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets
 1  _gateway (192.168.2.1)  0.523 ms  0.482 ms  0.501 ms
 2  1.2.3.4 (1.2.3.4)  29.994 ms  30.725 ms  30.475 ms
 3  * * *
 4  some_domain_1.com (5.6.7.8)  51.344 ms  51.593 ms  51.812 ms
 5  some_domain_2.com (9.10.11.12)  349.981 ms  350.202 ms  350.185 ms
 6  13.14.15.16 (13.14.15.16)  52.028 ms 17.18.19.20 (17.18.19.20)  52.280 ms  52.195 ms
 7  some_domain_3.com (21.22.23.24)  58.685 ms 25.26.27.28 (25.26.27.28)  67.073 ms  67.290 ms
 8  29.30.31.32 (29.30.31.32)  57.032 ms  67.212 ms  67.204 ms
 9  33.34.35.36 (33.34.35.36)  68.787 ms some_domain_4.com (37.38.39.40)  59.666 ms some_domain_5.com (41.42.43.44)  69.316 ms
10  108.170.251.129 (108.170.251.129)  67.338 ms 108.170.252.1 (108.170.252.1)  58.179 ms 108.170.252.65 (108.170.252.65)  69.634 ms
11  72.14.232.33 (72.14.232.33)  59.104 ms 209.85.251.239 (209.85.251.239)  68.459 ms dns.google (8.8.8.8)  58.002 ms

And here is the same traceroute, but with the laptop VPN enabled :

$ traceroute 8.8.8.8
traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets
 1  10.7.2.1 (10.7.2.1)  62.594 ms  74.503 ms  74.524 ms
 2  45.46.47.48 (45.46.47.48)  74.552 ms  74.547 ms  74.544 ms
 3  49.50.51.52 (49.50.51.52)  1152.730 ms  1164.535 ms  1164.447 ms
 4  53.54.55.56 (53.54.55.56)  74.465 ms some_domain_6.com (57.58.59.60)  74.468 ms 61.62.63.64 (61.62.63.64)  74.453 ms
 5  some_domain_7.com (65.66.67.68)  74.449 ms some_domain_8.com (69.70.71.72)  74.434 ms  74.429 ms
 6  google.equinix-ix.fr (195.42.145.65)  121.687 ms 108.170.244.225 (108.170.244.225)  72.067 ms google.equinix-ix.fr (195.42.145.65)  68.295 ms
 7  108.170.244.161 (108.170.244.161)  118.111 ms  173.570 ms 108.170.244.193 (108.170.244.193)  173.570 ms
 8  66.249.94.133 (66.249.94.133)  173.573 ms dns.google (8.8.8.8)  173.554 ms 108.170.235.37 (108.170.235.37)  173.542 ms

• My Question are :

  1. Can I tell that both VPNs are used by using those traceroute info ?
  2. If both VPNs are used, shouldn't I get more hops used in the 2nd traceroute ?
  3. Is there a more reliable way to test if both VPN are used ?
  4. (Edit) Are the "VPN passthrough" settings in my DD-WRT router involved in my questions ?

Answer 1

Can I tell that both VPNs are used by using those traceroute info ?

Just based on the traceroute this is not possible. You need at least to know what the endpoints of your VPN connections should be and check if these are shown in the traceroute.

If the router VPN is used these endpoint IP are the VPN entry (router) and exit (somewhere on the internet). If the laptop VPN is used the VPN entry is the local computer and the VPN exit is somewhere on the internet. If both VPN are used together it will exactly look like if laptop VPN is used only since the underlying carrier for the laptop VPN (i.e. the router VPN) is not visible from within the laptop VPN but only from outside.

If both VPNs are used, shouldn't I get more hops used in the 2nd traceroute ?

No, you should get the hops until the VPN entry (i.e. local laptop or router) and from the VPN exit (somewhere on the internet). Thus it depends on where exactly entry and exit are.

Is there a more reliable way to test if both VPN are used ?

You cannot see this way if the VPN are stacked. A packet capture on all the entry or exit points of the VPN would be more reliable.

Are the "VPN passthrough" settings in my DD-WRT router involved in my questions ?

Probably not. This should not be relevant for OpenVPN connections.