multiple network interfaces questions, RHEL 3 new install

[Rick Stevens]

Chuck Campbell wrote:
> After googling all afternoon, I begin to understand my earlier misconceptions
> :-)
> 
> On Fri, Jan 21, 2005 at 05:18:22PM -0600, Bob McClure Jr wrote:
> <snip>
> 
>>>Where can I find info on setting things up this way (or is it impossible) ?
>>>I know that I can bind samba to a particular interface, but how do I control
>>>what interface talks to the local intranet and what interface only talks
>>>to other cluster machines?
>>
>>Only by subnetting.  The port (Samba, mail, et al.) is irrelevant to
>>the ethernet device.  The network interface card cares only about IP
>>address.
>>
>>
>>>Will they need to be different sub-nets to make this work?
>>
>>Yes, if you don't want to mix differing traffic on the same wire.
> 
> 
> That's the goal.  The cluster machines should talk to each other (on their 
> own subnet) through the gigabit layer 3 switch in the machine room.  That 
> should enable isolation from other traffic, right?  

Yes, it will.

> In addition, I'll bind the second gigabit ethernet card to a different subnet,
> although it will plug into the same layer 3 gigabit switch in the machine room.
> This interface will be used for samba data serving to the local network.

That's fine.

> The layer 3 switch will uplink to the local network layer 3 gigabit switch.

Uh, huh.

> Does this get me to where I want to be, or am I still disillusioned.

No, as long as each NIC is on a separate subnet, traffic should be
segregated the way you want.

> ASCII drawing follows that shows what I HOPE to accomplish:
> 
> eth1 on cluster machines are subnet 1
> eth2 on cluster mnaster is subnet 2 (local network)
> 
> Cluster master does cluster management and computation
> Cluster slave(s) do computation
> Cluster master does samba serving
> 
> __________                        __________
> |  eth1  |-----|            |-----|  eth1  |
> | cluster|   __|____________|__   | cluster|
> | master |   | layer 3 switch |   | slave  |
> |  eth2  |---|    gigabit     |   |        |
> |________|   |________________|   |________|
>                     |
>              _______|__________
>              | layer 3 switch |
>              |    gigabit     |
>              |________________|
>                     |
>                _____|_________
>                | local net   |
>                |many machines|
>                |_____________|
> 
> 
> I assume I still need to do some routing configuration to make this work?

Well, no, not if the NICs are on different subnets.  As you add IPs in
different subnets to the NICs, the route table will automatically be set
up so that the IP on the machine is used as the route for that network.
When you're all done, a "netstat -rn" should show each network using a
different "Iface" part, with the "gateways" set up as "0.0.0.0".  The
default gateway will show up with a "gateway" as the IP of your default
route and will have a "G" in the "Flags" column.
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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-     Never put off 'til tommorrow what you can forget altogether!   -
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