[NTLUG:Discuss] Re: using the dsl and dial up connections at the same time

[Bryan J. Smith]

On Thu, 2004-10-28 at 10:58, David Evans wrote:
> yes I have a linux box that is out of state and the company is not going 
> to run dsl to it.

Then it's just a matter of routing and route distribution.  The latter
is the tricky party

The easiest way is to make sure your remote box connects to the same
system that is your "default gateway" from the standpoint of your LAN. 
Typically this is your 1-to-many NAT device (and limited firewall too).

There are 2 ways to do this:
  1.  Dial-up an ISP, then VPN over the Internet.  This is slowest.
  2.  Add a modem to the "default gateway" system

The reason you want to use the "default gateway" system is so your nodes
only need to know "one way in/out."  Otherwise, each and _every_ node on
the LAN that might communicate with any device that does _not_ go
through the "default gateway" will need to know about it.

That becomes either a manual procedure -- i.e., setting the routes
manually on each system -- or distributing them using a dynamic routing
protocol.

One I recommend you do _not_ do is do redirection on your NAT.  Don't
bother your NAT device.  Many people do this and it does _not_ work
reliably (especially not on those SOHO devices).  It can also cause all
sorts of ARP issues (not good).

So, what you need to do is distribute the route to your remote node
across your LAN.  Typically this is done with RIP or OSPF (RIP is fine
for small networks), although you _could_ set it manually in a startup
script.

If you have a "quality" firewall/NAT -- i.e., a _real_ router -- then it
could distribute the route via RIP or OSPF for you.  In fact, it might
have a nice web-based setup to define routes it will distribute via
RIP.  You'd be surprised how _cheap_ these things are these days -- I've
seen one sub-$200 with RIP.

Heck, I've seen a sub-$500 layer 3 switch capable of OSPF.


-- 
Bryan J. Smith                                  b.j.smith at ieee.org 
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