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Martin Thoma
Asked: 2012-11-21 03:30:53 +0800 CST

How can I see if I'm logged in via VPN?

  • 772

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?

command-line

5 Answers

  1. Best Answer

    Route-based VPN or overlay network solutions (with virtual interfaces)

    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

    Policy-based VPN (e.g. strongSwan)

    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
    • 25

  2. You can also check your routes with the route command. You will see more routes as normal and to different destinations.

    Example

    Connected without juniper:

    moose@pc07:~$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.0.0     *               255.255.255.0   U     2      0        0 wlan0
link-local      *               255.255.0.0     U     1000   0        0 wlan0
default         192.168.0.1     0.0.0.0         UG    0      0        0 wlan0

    Connected with Juniper:

    moose@pc07:~$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.0.1     *               255.255.255.255 UH    1      0        0 wlan0
vpn.kit.edu     192.168.0.1     255.255.255.255 UGH   1      0        0 wlan0
192.168.0.0     *               255.255.255.0   U     2      0        0 wlan0
link-local      *               255.255.0.0     U     1000   0        0 wlan0
default         vpn-cl-192-62.s 0.0.0.0         UG    1      0        0 tun0
default         192.168.0.1     0.0.0.0         UG    10     0        0 wlan0
    • 12

  3. In my case, the device is cscotun0 (I use Cisco Anyconect Secure Mobility Client) rather than tun0.

    Therefore (based on Terry Wang's answer and zipizap's comment), if you do not know the device name, you may use:

    if [ "0" == `ifconfig | grep tun0 | wc -l` ]; then echo "n"; else echo "y"; fi

    or, if you know the device name:

    if ifconfig cscotun0 &>/dev/null; then echo "y"; else echo "n"; fi

    UPD With Ubuntu 18.04, I need:

    if [ "`ifconfig | grep vpn0`" != "" ] ; then echo yes; else echo no; fi

    Unfortunately, ifconfig vpn0 now returns 0 (success) even if vpn is not working.

    • 3

  4. Alternative solution (Gnome)

    Check when it's running

    ➜ ifconfig -a | grep vpn | grep RUNNING
1:179:vpn0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1334

    Check when it's not running

    ➜ ifconfig -a G vpn
179:vpn0: flags=4240<POINTOPOINT,NOARP,MULTICAST>  mtu 1334

    so you can check for UP, RUNNING via grep as shown below

    ifconfig -a | grep vpn | grep RUNNING
vpn_running=$?

if [ $vpn_running -ne 0 ]; then

    echo "VPN <span color='yellow'><tt>UP</tt></span> | iconName=utilities-terminal-symbolic bash='nmcli con up id VPN' terminal=false"
else
    echo "VPN <span color='red'><tt>(DOWN)</tt></span> | iconName=utilities-terminal-symbolic bash='nmcli con down id VPN' terminal=false"
fi

    I'm using fantastic argo gnome shell plugin, and above is part of my script so I can launch VPN from toolbar (or shut it down)

    • 2

  5. Using the juniper ncdiag commands will give you this information.

    • Use ncdiag -t for a tunnel test.
    • Use ncdiag -h for host info.

    More specifics:

    $ cd ~/.juniper_networks/network_connect
~/.juniper_networks/network_connect$ file !$
file ncdiag
ncdiag: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.2.5, stripped
~/.juniper_networks/network_connect$ ./ncdiag 
    usage: ./ncdiag -A [or]
    usage: ./ncdiag -i -s -d -t -h -a -r <hostname> -k -v
     -A : All tests
     -i : installation test 
     -s : service test 
     -d : driver tests 
     -t : tunnel test 
     -h : host info 
     -a : adaptor test 
     -r : resolve host 
     -k : kill NC gui 
     -v : version   

~/.juniper_networks/network_connect$ ./ncdiag -t
+==============================================================================+
|   Tests:          |        Results:                      |
+==============================================================================+
       o  NC Diagnostics            
             NC Tunnel Test          Established

       Finished running tests 
+==============================================================================+
~/.juniper_networks/network_connect$ ./ncdiag -h
+==============================================================================+
|   Tests:          |        Results:                      |
+==============================================================================+

   o  Host Details              
         Hostname            tau
         Domainname          (none)
         IP Routing Enabled      Yes
         IP Loopback test        Passed
         Nameserver Details     
           8.8.8.8       Ping Passed

           8.8.6.6       Ping Passed
         Gateway Ping Test           
            10.20.20.1       Ping Passed

   Finished running tests

    +==============================================================================+

    • 1