Posted by: Anonymous Coward
on April 17, 2005 01:16 AM
I'm afraid that's not how it works. In the setup you describe, until the Linux box detects one of these Ethernet interfaces are down, at the Ethernet level, it will continue to send packets out that interface. The Linux box you describe has ethernet connections to routers "upstream" of it. Typically that router is customer premise equipment provided by the ISP. You have an Ethernet connection to it. It then has a connection to the ISP, via DSL, another Ethernet interface, etc. If if looses its link layer connection (DSL, Ethernet, wireless, etc.) on its WAN, you are still going to have an Ethernet connection between the Linux box and the CPE. The Linux box does not know there is a problem and continues to route out that inteface, as the previous poster said it would.
The previous poster also noticed something about your setup but only impied it, when he said you would lose half your packets. The setup you describe will not send traffic out one connection, and fail over to the second. All have you done is create to equal weight default routes. The Linux box will route out both interfaces, not one or the other, unless it detects one of the Ethernet inerfaces down, as discussed above.
You've started on the right track, but you have a a ways to go.