I use Juniper Networks (a Java program that establishes a VPN connection).
Does a command exist that lets me check if I'm logged in with Juniper?
If you run ifconfig -a or ip link show you should be seeing something like tunX below which is a tun device used by most route-based VPN:
# tun device
# used by route-based VPN
tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr: P-t-P: Mask:
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1300 Metric:1
RX packets:10 errors:0 dropped:0 overruns:0 frame:0
TX packets:24 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:1435 (1.4 KB) TX bytes:1677 (1.6 KB)
# Jan 2020 refresh
# sample ifconfig output with 3 virtual interfaces
# for route-based VPN or overlay network
nebula1: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1300
inet 172.16.87.100 netmask 255.255.255.0 destination 172.16.87.100
inet6 fe80::b2c4:4360:a3ae:15aa prefixlen 64 scopeid 0x20<link>
unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 500 (UNSPEC)
RX packets 37 bytes 2980 (2.9 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 331 bytes 17408 (17.4 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
tun0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1500
inet 172.16.200.1 netmask 255.255.255.0 destination 172.16.200.1
inet6 fe80::9d2e:5979:5ac2:43df prefixlen 64 scopeid 0x20<link>
unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 100 (UNSPEC)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1677 bytes 80496 (80.4 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
wg0: flags=209<UP,POINTOPOINT,RUNNING,NOARP> mtu 1420
inet 172.16.111.100 netmask 255.255.255.0 destination 172.16.111.100
unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 1000 (UNSPEC)
RX packets 37337578 bytes 10884991930 (10.8 GB)
RX errors 0 dropped 67878 overruns 0 frame 0
TX packets 60202096 bytes 66040772964 (66.0 GB)
TX errors 169 dropped 44429 overruns 0 carrier 0 collisions 0
ip link output
5: wg0: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1420 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
link/none
6: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN mode DEFAULT group default qlen 100
link/none
11: nebula1: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1300 qdisc fq_codel state UNKNOWN mode DEFAULT group default qlen 500
link/none
Or if you are using IPsec (e.g. strongSwan), ifconfig -a will show a tunnel device (tunX) like below if you are using Route-based mode (default is policy-based):
tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:192.168.11.2 P-t-P:192.168.11.2 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
If strongSwan is running policy-based routing (default), you'll be able to figure out by manipulating the kernel routing table or looking at ip-xfrm IP framework for transforming packets (encrypting payloads).
# manipulate kernel routing table for more info
ip r
route -nr
ip r show table main
ip r show table local
# strongswan specific table id 220
ip r show table 220
In addition, you can use ip tuntap show to see if there are tun/tap devices to determine if VPN is in use.
ip tuntap show
tun0: tun
