Interface Priority in the Face of VPN

Question

I have a few interfaces: wlan0, eth0, lo, and sometimes tun0. When I connect to the Juniper VPN, creating a tun0 interface, my existing connections on other interfaces (perhaps with the exception of lo) are interrupted, and they reconnect using the tun0 interface.

I only want to use tun0 on particular connections of my choosing, not all of them, and not by default. How can I ensure that the default interface is eth0 or wlan0? The output of ip addr is here:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
    link/ether d4:be:d9:65:c1:45 brd ff:ff:ff:ff:ff:ff
3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 24:77:03:ab:a6:dc brd ff:ff:ff:ff:ff:ff
    inet 10.23.4.5/24 brd 10.23.4.255 scope global wlan0
       valid_lft forever preferred_lft forever
    inet6 2601:d:a780:2c3:f803:d084:a01f:f156/64 scope global temporary dynamic 
       valid_lft 86397sec preferred_lft 14397sec
    inet6 2601:d:a780:2c3:2677:3ff:feab:a6dc/64 scope global dynamic 
       valid_lft 86397sec preferred_lft 14397sec
    inet6 fe80::2677:3ff:feab:a6dc/64 scope link 
       valid_lft forever preferred_lft forever
5: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1400 qdisc pfifo_fast state UNKNOWN group default qlen 500
    link/none 
    inet 140.182.72.57/32 scope global tun0
       valid_lft forever preferred_lft forever

Source: http://sprunge.us/KKGP

I noticed that tun0 is on the bottom, so I would think it's bottom priority, too?

NOTE: For what it's worth, I don't know how to modify the priority of the other interfaces either (eth0, wlan0, lo).

Answer 1

It not about interface priority. The routing table determines what path your traffic will take. See ip route show and ip route get ipaddress

Most VPNs push a default route via themselves. In my OpenVPN setup I've configured it to only push routes to the internal IP space, however that is a server-side option.

Your client may offer the option of ignoring the pushed routes and specifying your own.