Network Traffic Generation

[Daniel Feiglin]

Oleg Goldshmidt wrote:
> Shachar Shemesh <shachar at shemesh.biz> writes:
>
>   
>> Do the following experiment. Connect the 100 card to a network, and
>> from another computer ping the 101 address while a sniffer is
>> running. You will see an ARP reply going out from the 100 card,
>> carrying the 100 MAC address, and the ping will succeed despite the
>> 101 card being disconnected. Why? Because the computer says "I know
>> how to reach 101 - it's my IP, so if the ARP reached the 100 card,
>> it's probably a good MAC address to respond with".
>>     
>
> Let me first make a disclaimer that I have not tried it myself in this
> configuration, but here is what *might* point you towards a
> solution. It may also turn out a dead end, mind you.
>
> Try to use iproute2 to created multiple routing tables by policy. In
> principle, iproute2 should enable you to create multiple routing
> tables per process (you need "policy routing" enabled in the kernel,
> too). Configure routing rules per destination host in such a way that
> traffic intended to 101 goes out of device eth0, and traffic intended
> to 100 goes out of device eth1.
>
> Google for more descriptions and explanations for "multiple default
> gateways linux" or some such. Some links that (say similar things and)
> may be of help are
>
> http://www.clintoneast.com/articles/multihomed.php
> http://lartc.org/howto/lartc.rpdb.multiple-links.html
> http://linux-ip.net/html/adv-multi-internet.html
> http://kindlund.wordpress.com/2007/11/19/configuring-multiple-default-routes-in-linux/
>
> Once again, I am not saying it is a solution for you problem, just
> something that might help you work it out, if it is at all possible.
>
>   
>> The most immediate solution is to run a virtual machine, and give it
>> exclusive access to one of the NICs. This way you can configure, for
>> example, the 100 address in the real machine and the 101 address in
>> the virtual one.
>>     
>
> But this does not necessarily mean packets will go out of the machine
> - hypervisors include local (in-box) switching nowadays.
>
>   
It seems that I've unintentionally opened a Pandora's Box with this one.
For the moment I've grabbed the iproute2 "howto" , which is available
from one of Oleg's links, above. (It's installed on all 3 of my Linux
boxes by default.)

Heavy homework for what I'd hoped was a rather simple problem!

About using virtual machines: (1) It's heavy fisted -  even if it works
(2) It's self defeating - My 2 Linux "test" boxes are each P IIs with
limited memory running a minimal SuSE 9.2 installation.

Enough for now.

D


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