Re: cups relaying remote broadcasts to a local subnet (SOLVED)

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On Thu, 2006-05-25 at 08:11 -0500, Gregory P. Ennis wrote:
> On Thu, 2006-05-25 at 00:12 -0700, Thomas Taylor wrote:
> > On Wednesday 24 May 2006 09:35, Gregory P. Ennis wrote:
> > >>>>> snip <<<<<
> > > >
> > > > This sounds like an application that could use a vpn (virtual private
> > > > network) over the internet.  I haven't done this yet but have seen it
> > > > used at one company.  You should be able to get information from the LPD
> > > > howto's on vpn or try googling for vpn.
> > > >
> > > > HTH,
> > > > Tom
> > > >
> > > > --
> > > > Tom Taylor
> > > > Linux user #263467
> > > > Federal Way, WA
> > >
> > > Tom,
> > >
> > > I have not set up a VPN yet either and had wondered the same thing.
> > > Does this mean you believe that cups is not designed to perform in the
> > > way I the network designed?
> > >
> > > I thought cups was a little more robust than that!!!
> > >
> > > Greg
> > 
> > To the best of my knowledge, cups has no way of communicating with a remote 
> > network without using a vpn.  
> > 
> > The 10.x.x.x series of IP addresses is set aside as private address space.  
> > Probably millions of people use it in their internal networks.  How is cups 
> > to know which 10.x.x.x to communicate with over the internet?  It can 
> > communicate with any allowed private address including subnets within as long 
> > as their is a direct physical or wireless connection.  It can't go out over 
> > the internet to find a private address space without a "tunnel" through the 
> > internet (between two internet portals)
> > 
> > If this doesn't make sense, think about how you would control a "remote" 
> > computer.  You would need to send a control signal (hopefully encoded) 
> > through your portal (your gateway to your ISP).  That signal would have to 
> > know how to find the portal for the remote you wanted to control.  Then you 
> > would have to connect to the internal network on the remote whose IP you can 
> > supply to cups.  What cups doesn't know is how to make a connection between 
> > the portals.  That's where the vpn (the tunnel) comes in.  It makes a 
> > connection between the internal network at one site and the internal network 
> > at another remote site and carries the communication over it.
> > 
> > I suspect that if you ask about how to set up the vpn like this on the list, 
> > you will get some better responses than I have given.
> > 
> > Tom
> > 
> > -- 
> > Tom Taylor
> > Linux user #263467
> > Federal Way, WA
> > 
> 
> Tom,
> 
> Thank you for taking the time to help me.  I have wanted to set up a VPN
> for awhile anyway, so now would he a good time to start the study
> process.
> 
> In regards to your comments about cups, I understand what you are
> saying, but my thought was that the documentation of cups seems to
> support the feature of local broadcasting from a gateway.  This
> certainly works for one of my units (the one with only one ethernet
> card), but as per your comments above it is placed on the same subnet as
> the network and would be expected to work.
> 
> There is still a lot of magic in the way tcp/ip communication occurs for
> me, but I was hopeful that cups would work in the same manner as httpd
> behind the gateway which allows communication to a desktop behind the
> firewall.  
> 
> I will take your VPN challenge, but do some studying before I post
> laughable questions.   
> 
> Thanks again for your help!!!!
> 
> Greg

Tom,

I finally figured out the solution.  The previous note you gave me was
very helpful, and it caused me to integrate some information gleaned
from a call to cups 'guys' of a week ago.

All I had to do to solve the problem was to 'add' the desired remote
printers to the gateway machines that pointed to the the printers inside
the local network.  ie ipp://machine.domain.com:631/printers/lpt0 should
be used to point to the name of the printer that is on the subnet inside
the gateway.

In summary for cups to work through a two ethernet card machine: 

1. If a printer is attached to one of the desktop machines inside the
local network the desired printer has to be set up not only on the local
machine, but also on the gateway machine.  

2. If a printer is directly attached to the network using a JetDirect
port 9100 it only has to be set up on the gateway machine.  

The gateway machine can then broadcast each kind of printer information
remotely as well as locally.

I hope this post saves some time for others trying to do the same thing.

Greg


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