PPP Lan Bridge

[Brian Somers]

On Mon, 21 Mar 2005 18:27:58 -0600, "Chris Tusa at Linisys, LLC" <linisys at gmail.com> wrote:
> Greetings,
> 
> I am an experienced BSD administator. I am currently implementing a
> solution to connect two campus area buildings together using 2
> machines running FreeBSD 5.3 with 56K modems & PPP.  I need some
> assistance as follows. I am trying to be verbose so as to provide a
> complete overview of what has been done and so this thread may be used
> a future guide for others.
> 
> Scenario:
> 
> * A countryclub has a maintainence department located on the other
> side of the golf course, too far to have a cable run or a
> line-of-sight wireless connection.  The purpose of this connection is
> to provide a TCP/IP timeclock with access to the main building's
> network to transmit data.
> 
> * Maintainence Shed (client): FreeBSD 5.3 client, Serial 56K modem
> running ppp-user. Timeclock connected to dial-up client via CrossOver
> ethernet cable.
> 
> * Clubhouse (server): FreeBSD 5.3 server, Serial 56K modem running
> mgetty. Server connected to LAN switch.
> 
> * The LAN at the clubhouse consists of a CABLE Modem connection, with
> an OpenBSD based firewall that provides NAT/PROXY services to the
> internal network.
> 
> Current Setup:
> 
> (see this diagram I posted:  URL =
> http://people.linisys.com/ctusa/images/diagram.jpg  )
> <img src="http://people.linisys.com/ctusa/images/diagram.jpg">
> 
> * main WAN router= 192.168.1.1
> * dialup Server (fxp0)= 192.168.1.230  gateway_enable="yes"
> * dialup Server (tun0)= 192.168.1.230 -> 192.168.1.232  (modem)
> * dialup Client (tun0)= 192.168.1.232
> * dialup Client (fxp0)= 192.168.2.1  gateway_enable="yes"
> 
> 
> Problem:
> 
> * It seems that NAT is functioning well, and the systems behind can
> communicate. However, the timeclock is unable to communicate with its
> counterpart at the clubhouse. I believe this is because they are on
> different subnets and routing is not taking place.
> 
> * The timeclock communicates on port 3301 - some sort of forwarding
> must be enabled through the ppp nat ?
> 
> * how can the 192.168.2.0  network be accessible from the 192.168.1.0 
> network?  I know that the 192.168.1.232 (modem) / 192.1681.230
> (ethernet)  server box at the main clubhouse is the gateway. How can
> other machines find out about this? or can the man residential gateway
> learn about this?
> 
> Current possible diagnosis:
> 
> * The complexity of having 2 gateways, it seems that in order for each
> machine to be able to see the 192.168.2.0 network at the client side
> (maintainence shed), a static route must be added. I would like to
> avoid this.
> 
> What I would like:
> 
> * To have the timeclock be on the SAME network as the rest of the clubhouse.

The issue is that 192.168.1.0/24 machines have to know to route
192.168.2.0/24 stuff through 192.168.1.230, or else the timeclock
machine needs some sort of presence on 192.168.1.0/24.

This can be done by allocating a segment of 192.168.1.0/24 to the ppp
client and adding ``enable proxyall'' to the ppp server config.

server:
  enable proxyall
  set ifaddr 192.168.1.230 192.168.1.232/30

client:
  set ifaddr 192.168.1.233 192.168.1.230

and then setting the addresses on the crossover cable to 192.168.1.233
and 192.168.1.234.

The ``enable proxyall'' bit tells ppp to create proxy arp entries for
all of 192.168.1.232/30 (except for .232 and .235), allowing everything
else on 192.168.1.0/24 to think it's talking directly to these machines.

-- 
Brian Somers                                          <brian at Awfulhak.org>
Don't _EVER_ lose your sense of humour !               <brian at FreeBSD.org>