Let's say i have two linux boxes, RouterA and RouterB, both with two NICs (eth0 and eth1).
RouterA/eth0 is connected to an internet uplink. RouterA/eth1 and RouterB/eth1 are directly connected.
What I'd like to do is plug the uplink to both RouterA/eth0 and RouterB/eth0, the latter being down (and without using any SPoF component like a switch, juste something passive). If RouterA goes down, RouterB will know it, and so it can bring it's eth0 NIC up.
But it seems such a passive link sharing device doesn't exist, according to the following comment of another thread (Connect two routers to a single uplink for full redundancy) :
"A passive Ethernet ATS does not exist because there mandatorily must be intelligence inside the device to determine whether the carrier signal of Ethernet is present or not. (It's not like a electrical ATS that just sees voltage.) That intelligence then introduces new electronics and software that can fail, thus canceling out any added benefit of the ATS. This type of ATS could be created, but nobody would buy it, therefore it is not created, manufactured, distributed, and sold at stores."
So, my question : does everybody agree with that ? Is there really no passive way to distribute an uplink between two routers, one being passive (NIC down) ? Something like a link duplicator, that sends the uplink to both RouterA/eth0 (up) and RouterB/eth0 (down). No risk of collision, RouterB/eth0 being down. And if RouterA/eth0 goes down, then RouterB/eth0 goes up
Right now, if RouterA goes down, I have to physically go the there to unplug the uplink cable and plug it into RouterB.