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From: Andy Furniss on 13 Apr 2008 18:32
Eric B. wrote:

> I have already read through what seemed to be the relevant sections, but
> unfortunately, am no further ahead. Specifically, sections 3, 4 and 11, but
> from everything I read, they all seem to be pointing to configuration on a
> per device basis. Given that eth0:0 is only a virtual device,

I don't think you could even call it a virtual device. It's just the way
ifconfig let you add secondary addresses to nics. ip just uses what it
calls secondary addresses (though there is a way to add labels that look
like the ifconfig way IIRC)

> the ip tool
> doesn't seem to like it very much. From what I can tell, it seems as though
> I have to mark the packets on the way in from gw1 differently than those
> coming in from gw2, and then use the ip route to add different gateways
> based on the routing table, but again, I am having trouble understanding how
> to do this with a single device only.
>
> Any ideas?

I've never done anything like this. Have a look on

http://www.linux-ip.net

as an alternative to LARTC.

Andy.
From: Andy Furniss on 13 Apr 2008 19:42
Eric B. wrote:
> Hi,
>
> I've got a computer running RHEL with a single NIC that is multi-homed with
> a single default gateway for everything.
> eth0: 192.168.101.54/24
> eth0:0 192.168.104.54/24
>
> So far, everything is running fine. The machine is able to respond to
> requests coming in to 101.54 and 104.54 without any problems.
>
> However, I have now reached a situation where I need to route my response
> packets to 2 different gateways, based on where the packets came in from.
> All packets that came in to eth0 have to be routed out via gateway1 and all
> packets that came in on eth0:0 have to be routed via gateway2.
>
> How can I accomplish this? I've tried reading the lartc howto for routing
> for multiple uplinks/providers, but it doesn't seem to address my issue.
> The howto for split access seems to require 2 independent NICs. When I try
> to follow the instructions, the ip route add command complains that it
> doesn't recognize eth0:0 as a valid interface.
>
> Is there any thing I can do? Can anyone point me to the right place to look
> for this? I'm assuming that it shouldn't be too difficult to configure the
> system to respond differently based on the incoming address, but not quite
> sure how to approach the situation.

I am unsure of your setup - if this box is the default gateway for
others then the addresses on your nic won't be involved - just the mac
address which will be the same as you only have one nic. I guess you
will need to use the source address of the incoming packet to tell where
it came from.

Andy.
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