My guess from other experience with the Cisco VPN client:

   1. ROS resolved your hostname to an IP, let's call it 192.168.1.15
   2. ROS tries to contact 192.168.1.15 when starting up roscore
   3. VPN client, ever so helpfully, routes ALL network traffic through the
   tunnel regardless of destination subnet
   4. VPN server end has no idea where to route a message to 192.168.1.15
   5. ROS cannot connect, as the VPN isn't routing requests back to your
   machine

I'd expect this problem to affect most anything using a VPN that isn't there
for the purpose of connecting to a rosmaster.

As you discovered, getting ROS to route things through the loopback
interface should bypass the VPN tunnel.

- Eric

On Wed, Sep 15, 2010 at 12:22 PM, Ken Conley <kwc@willowgarage.com> wrote:

> FYI: altering an error message is generally not a good idea. In this
> case, you're disguising the one piece of information that is useful
> for debugging in this case.
>
> This is basically a network configuration problem. Without knowing
> what your actual network config is, it's hard to provide a solution.
> As a general strategy, network configuration problems are generally
> resolved by setting ROS_IP to the IP address of the configuration
> you're binding to, or to set ROS_HOSTNAME to a hostname that resolves
> correctly across multiple configurations.
>
>  - Ken
>
> On Wed, Sep 15, 2010 at 9:07 AM, trinighost <trinighost@gmail.com> wrote:
> >
> > Hello Ken,
> > I changed the machine name for the post.. but the message does show my
> > actual machine name (not localhost).
> >
> > ROS_MASTER_URI is currently set to.
> > http://localhost:11311
> >
> > The other variables are blank/not set.
> > And it doesn't matter whether the machine is on a wired or wireless
> network.
> > --
> > View this message in context:
> http://ros-users.122217.n3.nabble.com/ROS-and-virtual-private-networks-tp1480052p1480777.html
> > Sent from the ROS-Users mailing list archive at Nabble.com.
> > _______________________________________________
> > ros-users mailing list
> > ros-users@code.ros.org
> > https://code.ros.org/mailman/listinfo/ros-users
> >
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