Cisco Serial Console cables are simply DB9 to RJ45. Of course many people have now come to use a variety of DB9 to USB adapters to get around many machines not having serial ports. But I'm more concerned with the RJ45 side and splitting that somehow.
Are there any known Dual RJ45 to single DB9 connections; is it even possible? I'd like to be able to manage two console connections to a single machine.
It's really not going to work like that. Think about what you asked for a moment.
They are RJ45, but it's still standard RS232, hence why it's converted to DB9. That means you have a TX line and RX line. If you have one computer side DB9 spliced to two RJ45s then your best case on what you're actually going to do is send both consoles the same keystrokes and you'll receive a garbage mix of both. Think of it like trying to use two phones at once... you hear both conversations at once, they both hear what you're saying, but they can't hear each other. How many times do you have to say "no I didn't mean you Alice, I meant Bob"?
Your approach of sticking multiple usb serial dongles on a single machine is probably the best way to approach it, though telnet/ssh access to the switches is a good option if you can go with it.
There do exist serial console switches that are analogous to KVM switches, they're priced similarly too. They do the job well if you can afford them though.
This may be silly to even post, instead of just deleting the question, but it may help someone in the future. I started thinking about ways to put it in a KVM and start splitting/sharing it that way. And then it hit me:
I can just use two console cables with two USB adapters to plug into a single machine with multiple USB ports.