Linux routing question

Good morning,

I have a linux routing question to ask. I am working on a linux server,
slackware 10.2 w/2.6.16 kernel, that has 2 ethernet cards in it. This
server is used for network monitoring of a LAN with mrtg and nagios. The
first NIC, eth0, is connected to a switch in the DMZ and has a public
routable IP address to the internet. The second NIC, eth1, is connected to
the internal network switches and has a private 10.x.x.x address to the
local LAN. The default route as of right now points to the internet
gateway router which is what I want. I have a network route set up on the
linux server to the 10.0.0.0 subnet for eth1 to talk to devices in the
private network. So as of right now I can ping and talk to everything I
need to.

Now, here is the wrinkle, this server does device failure notifications via
e-mail to specific persons. If the primary internet connection fails,
obviously, the notifications will not make it anywhere. I have learned
that there is a second internet connection available at a remote office. I
can contact that remote office network through the internal lan routing
with ping and my question is, how can I make this linux server routing
automatically fail-over to use that secondary internet connection if the
primary connection fails?

I am working on this server from 400 miles away where it is physically
located and would prefer to not have to call them to reset it 10,000 times
when I dink the routing table trying to figure it out.

Here is a copy of my current routing table as of right now, I have replaced
any public IP address info with XXX.XXX.XXX.XXX for obvious reasons.

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
localnet * 255.255.255.240 U 0 0 0 eth0
10.1.2.0 * 255.255.255.0 U 0 0 0 eth1
10.0.0.0 10.1.2.254 255.0.0.0 UG 0 0 0 eth1
loopback * 255.0.0.0 U 0 0 0 lo
default XXX.XXX.XXX.XXX 0.0.0.0 UG 1 0 0 eth0

Any idea's would be great,
Thanks,
Dave
.

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