Packet "Mixing" Between Multiple NICs on Host

[Christopher K. Johnson]

Jonathan B. Horen wrote:

>
> Is there a way to configure routing on this server so that a packet's 
> source-address is "honored" by the system when responding?
>
There are some details lacking, such as what are the addresses of the 
workstations.  In particular the workstation that was pinging in your 
example.

Here is what I think is happening:  The metric field is ignored, but 
when routes handle duplicate destinations (in this case default or 0/0) 
the last one added  prevails in my experience.

If the workstations were local the interface device routes should 
prevail.  So I am guessing that you pinged the name server address from 
a different subnet from any in your route table, and the last interface 
brought up's associated route-ethx defined route is how the response was 
sent.

Try this experiment:
ifdown eth0
ifup eth0

I think you will see all packets to non-local subnets go through eth0 
via 128.139.197.16.

There is no harm in either configuration unless you believe one default 
route is a faster way to get there, or not all the same subnets are 
accessible via either gateway.

If the former is true, then remove the route-ethx file for the slow 
gateway route.
If the latter is true, then you need to put more specific routes in each 
of the route-ethx files, not simply designate both of them as default.

There are routing daemons available if there are routing protocols 
supported by your gateways through which the server can learn the most 
effective route to a destination.  See the quagga package included in 
fedora core.

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   Chris Johnson, RHCE #807000448202021