> If your OOB network is your only way of managing things, you not only have to build a separate network, you have to make sure it is fully redundant, because otherwise you've created a single point of failure for (some) management.
I'm not sure I necessarily agree with that. You can set up the network in such a way that you can route over the main network as a backup if your OOB network was down but the main network was up. Obviously, it's not quite as simple as sticking a patch cable between the two networks, but it can be close - you have a machine that's always on your OOB network, and it has an additional port that either configures itself over DHCP or has a hard-coded IP for the main net. But the important thing is that you never have that patched in, except for emergencies like your OOB network cable being severed but you still have access to the main network. If that does happen, you plug it in temporarily and use that machine as a proxy. There's no real reason for extra redundancy in the OOB, because if your main uplink is also severed, there's not really much you're going to be usefully configuring anyway!
> If your OOB network is your only way of managing things, you not only have to build a separate network, you have to make sure it is fully redundant, because otherwise you've created a single point of failure for (some) management.
I'm not sure I necessarily agree with that. You can set up the network in such a way that you can route over the main network as a backup if your OOB network was down but the main network was up. Obviously, it's not quite as simple as sticking a patch cable between the two networks, but it can be close - you have a machine that's always on your OOB network, and it has an additional port that either configures itself over DHCP or has a hard-coded IP for the main net. But the important thing is that you never have that patched in, except for emergencies like your OOB network cable being severed but you still have access to the main network. If that does happen, you plug it in temporarily and use that machine as a proxy. There's no real reason for extra redundancy in the OOB, because if your main uplink is also severed, there's not really much you're going to be usefully configuring anyway!