Since you have a physical loop in your topology, in order to stop it you need to use STP. The other alternative is Flex Link if your devices support it. With Flex link you are still using one link as primary and one as backup.
Correct, STP will block one link to prevent loop. Now, in your example if switch B and C are 3750 series switches, you can stack them together and connect switch A to both switch B and C using an Etherchannel. In this case you utilize both links.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...