Many diigital consoles use protocols that cannot go through ethernet switches. That is the case with the OP's Soundcraft running MADI/AES 10. It's also true for Behringer's AES 50, and a host of others. They are simply not compatible with computer industry hardware. Redundancy is easy with systems running on a Dante network.
I agree with you on having more than one cable. Cat 5 cables are fragile no matter who makes it or whether it is considered rugged. Because the show depends on it, a second cable should always be available.