[LARTC] Forcing an "external" route

[LARTC] Forcing an "external" route

[David Purves]

Here is as wacky a situation as you might find...

    Given a linux box with two ethernet cards:
        eth0  at ip 192.168.100
        eth1 at ip 172.16.1.100,
    and an internet "appliance" with two ethernet ports:
        p0 at ip 192.168.1.101
        p1 at ip 172.16.1.1,

    I want to force packets from     eth0 <--> eth1     to take the path 
    eth0 <--> p0 <--> p1<-->eth1.

What I have here is an appliance that I want to run some throughput tests.

The cables are set up eth0 <--> p0 and p1<-->eth1 and work (pings work 
just fine)....
    no matter what I try, the kernel is too smart for me  :-) , and it 
routes internally (inside the linux box) instead of entering the outside 
world.

Any ideas?

David Purves


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Re: [LARTC] Forcing an "external" route

[bert hubert]

On Fri, Dec 07, 2001 at 03:38:48PM -0600, David Purves wrote:

>     I want to force packets from     eth0 <--> eth1     to take the path 
>     eth0 <--> p0 <--> p1<-->eth1.
> 
> What I have here is an appliance that I want to run some throughput tests.
> 
> The cables are set up eth0 <--> p0 and p1<-->eth1 and work (pings work 
> just fine)....
>     no matter what I try, the kernel is too smart for me  :-) , and it 
> routes internally (inside the linux box) instead of entering the outside 
> world.

I don't think that this is possible purely with iproute2. You will probably
need at least one extra machine to perform NAT.

Perhaps you can get away with UML (usermodelinux).

Regards,

bert

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Re: [LARTC] Forcing an "external" route

[bert hubert]

On Fri, Dec 07, 2001 at 04:46:00PM -0600, Greg Scott wrote:
> What if you used some iptables rules to DENY packets from eth0 with
> destination ip address 172.16.1.100?  I'm thinking you might have to put in
> the rules in the OUTPUT table and catch them on the way out from
> 192.168.1.100.  No clue whether or not that will work, but worth a try.

That just drops the packets. You might try some DNAT stuff on the iptables
POSTROUTING chain, perhaps that works. I think it might.

Regards,

bert

-- 
http://www.PowerDNS.com          Versatile DNS Software & Services
Trilab                                 The Technology People
Netherlabs BV / Rent-a-Nerd.nl           - Nerd Available -
'SYN! .. SYN|ACK! .. ACK!' - the mating call of the internet

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RE: [LARTC] Forcing an "external" route

[Greg Scott]

What if you used some iptables rules to DENY packets from eth0 with
destination ip address 172.16.1.100?  I'm thinking you might have to put in
the rules in the OUTPUT table and catch them on the way out from
192.168.1.100.  No clue whether or not that will work, but worth a try.

- Greg



-----Original Message-----
From: David Purves [mailto:davidpurves@mindspring.com]
Sent: Friday, December 07, 2001 3:39 PM
To: lartc@mailman.ds9a.nl
Subject: [LARTC] Forcing an "external" route


Here is as wacky a situation as you might find...

    Given a linux box with two ethernet cards:
        eth0  at ip 192.168.100
        eth1 at ip 172.16.1.100,
    and an internet "appliance" with two ethernet ports:
        p0 at ip 192.168.1.101
        p1 at ip 172.16.1.1,

    I want to force packets from     eth0 <--> eth1     to take the path 
    eth0 <--> p0 <--> p1<-->eth1.

What I have here is an appliance that I want to run some throughput tests.

The cables are set up eth0 <--> p0 and p1<-->eth1 and work (pings work 
just fine)....
    no matter what I try, the kernel is too smart for me  :-) , and it 
routes internally (inside the linux box) instead of entering the outside 
world.

Any ideas?

David Purves


_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO:
http://ds9a.nl/2.4Routing/

_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://ds9a.nl/2.4Routing/