Dual homed, non-routing Linux configuration

Dual homed, non-routing Linux configuration

Post by Dan Peterk » Sat, 13 Jun 1998 04:00:00



Hi,

I have my Linux box connected to two different networks, and I don't
want to have the Linux box routing anything, so I've turned off IP
forwarding. Each of the two Ethernets have gateways to the outside world
and I want the computer to have access to sites available from both
sides. I've got a default route that points to a router on one Ethernet
side, but how do I go about getting the other Ethernet card to work for
sending traffic out the gateway on its side? Can I turn on routed
without having it route traffic between the ethernet cards, but still
have the gateway router on this side use RIP to teach the Linux box
about routes available out of the non-default Ethernet interface?

--
____________________________________________
  Dan Peterka

 
 
 

Dual homed, non-routing Linux configuration

Post by Michael Clar » Sat, 13 Jun 1998 04:00:00



> Hi,

> I have my Linux box connected to two different networks, and I don't
> want to have the Linux box routing anything, so I've turned off IP
> forwarding. Each of the two Ethernets have gateways to the outside world
> and I want the computer to have access to sites available from both
> sides. I've got a default route that points to a router on one Ethernet
> side, but how do I go about getting the other Ethernet card to work for
> sending traffic out the gateway on its side? Can I turn on routed
> without having it route traffic between the ethernet cards, but still
> have the gateway router on this side use RIP to teach the Linux box
> about routes available out of the non-default Ethernet interface?

> --
> ____________________________________________
>   Dan Peterka

Have you tried setting two default routes??  I am not sure it this will
solve all of your issues, but it is easy to try.  :-)

mc

 
 
 

Dual homed, non-routing Linux configuration

Post by floyd » Sun, 14 Jun 1998 04:00:00




> > I have my Linux box connected to two different networks, and I don't
> > want to have the Linux box routing anything, so I've turned off IP
> > forwarding. Each of the two Ethernets have gateways to the outside world
> > and I want the computer to have access to sites available from both
> > sides. I've got a default route that points to a router on one Ethernet
> > side, but how do I go about getting the other Ethernet card to work for
> > sending traffic out the gateway on its side? Can I turn on routed
> > without having it route traffic between the ethernet cards, but still
> > have the gateway router on this side use RIP to teach the Linux box
> > about routes available out of the non-default Ethernet interface?
> Have you tried setting two default routes??  I am not sure it this will
> solve all of your issues, but it is easy to try.  :-)

nope... this will not work.. cause it still doesn't know which way to send
it.i'm having a similar problem with a slightly different twist.  i have 1
machine with 2 modems and 2 dialup connections.... this is all well and good
except that my ISP doesn't support modem-bonding and i don't have the cash for
one of the stand-alone dojobbies.

now, i don't really need to have bonded modems, what i would liek to do is
have 2 virtual networks and route each through its own ppp connection.  again,
though, one runs into the default route problem.  i tried using ipfwadm
direction all traffic from one netwokr to a specific interface but cound't
make it work.. am i on the right path?

-floydd

 
 
 

Dual homed, non-routing Linux configuration

Post by Raymond Doetje » Thu, 18 Jun 1998 04:00:00


Very easy Peterka,

You have to add a static route for your client to the other network segment
were your router is attached. Or even easier just configure the default
gateway adress for your host to that router. This also prevents users on
the other subnet to browse on the other subnet (hmm????)
Your client (multi-homed server) knows both IP stacks, and so also uses
it's internal routing to get to the other segment using your defaukt
gateway.


> Hi,

> I have my Linux box connected to two different networks, and I don't
> want to have the Linux box routing anything, so I've turned off IP
> forwarding. Each of the two Ethernets have gateways to the outside world
> and I want the computer to have access to sites available from both
> sides. I've got a default route that points to a router on one Ethernet
> side, but how do I go about getting the other Ethernet card to work for
> sending traffic out the gateway on its side? Can I turn on routed
> without having it route traffic between the ethernet cards, but still
> have the gateway router on this side use RIP to teach the Linux box
> about routes available out of the non-default Ethernet interface?

> --
> ____________________________________________
>   Dan Peterka

 
 
 

1. Non-routing firewall configuration

I'm hoping to set up a linux/ipchains firewall on a dedicated
machine (no proxy/masquerading etc) but I dont want this
machine to have to be my default router. My lab is on a
branch of a campus ethernet which provides routing to the
internet and all I want to do is apply filters to the stuff between
my lab and the campus, see diag.

Uni Campus
(Class B)                           __________
------------------------|----------| My f/wall|-------My lab ethernet
                        |                             (part of uni class B)
                   -----------------
                   | Uni routers    |
                   | which are also |
                   | my default rtrs|

My firewall box has a pair of ethernet adapters, but how do I get
traffic to be transferred from one to the other (after passing the
ipchains checks) without involving routing?
I have seen a suggestion (HOWTO/mini/Bridge) to turn the f/w machine
into a bridge (compile a kernel with BRIDGING enabled) and then
put both adapters into promiscuous mode. Will this do the trick?
At what point in the networking does the firewall filtering get
applied. Is it to every packet as it comes in/goes out of the
ethernet adapters or is it during the routing process? Or am I
about to become a kernel hacker?

Cheers
Terry.


Computer Manager
Medical Research Council
Lab of Molecular Biology
Hills Road
CAMBRIDGE CB2 2QH
U.K.

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