[PLUG] Routing question

alan alan at clueserver.org
Sat Feb 26 07:29:50 UTC 2005


On Fri, 25 Feb 2005, Rich Burroughs wrote:

> Russell Senior wrote:
> 
> > On machines on network A you need to have a route for network B point
> > to the machine in-between, and vice versa.
> > 
> > I don't have a complete picture of your network.  Can you provide
> > ASCII art or similar.  
> > 
> > If the default gateway is the in-between machine then it should just
> > work without anything special.  Occasionally I have been screwed up if
> > particular /proc/sys/net/ipv4/conf/<foo>/forwarding was set
> > incorrectly.
> 
> Yeah, it would help to see a diagram.
> 
> Normally this kind of setup would be pretty easy, and wouldn't require 
> brodcasting routes. You just put two NICs in the router box, and assign 
> one an address from Network A and the other an address from Network B. 
> Then on the clients you make the NIC in their network the gateway. The 
> startup scripts on the router box should set all the routes that are needed.
> 
> But that all assumes the router box is also the Internet gateway, if 
> there is one. Depending on your setup you might need something more 
> complex, it's hard to say without more info.
> 
> Forwarding does need to be on, as Russell mentioned.

It is a bit more difficult than that.

Here is what I am dealing with...

Network A is a bunch of Mac OS X machines.

Network B has a spiffy Ricoh multifunction scanner/printer/fax uberprinter 
that they want to use from network A.  I have mapped out the ports that it 
responds to, but it looks like this thing can connect out to machines on 
its own.

Internet GW (10.0.1.1)       Internet GW (10.1.1.1)
   |                                |
Network A (10.0.1.0/24)      Network B (10.1.1.0/24)
   |                                |- printer (10.1.1.220)
   |------- 10.0.1.220 (eth0)       |
                |              10.1.1.221 (eth1)
                |--- Slackware Box -|

I can't force static routes on the other machines because I do not control 
them.  I would only need to do that on Network A as Network B is fine on 
its own, except for routing back from the printer. If I did not have to 
worry about the scanner connecting back, I would just nat between the 
two.

I have done something similar to this 10+ years ago, but it was on 
Solaris.

-- 
Q: Why do programmers confuse Halloween and Christmas?
A: Because OCT 31 == DEC 25.




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