I have a network built with 5 3560 switches. They are linked together over 6 fiber gigabit links. Two of them are for redundancy. I set up STP and all works fine. STP root is on the same switch for all VLANs.
But I'm wondering why blocked links are only show state blocked on one of the two connected switches. I've read the docu but didn't found a hint.
I guess your question in fact translates to: why is there only one side of my redundant link that is blocking instead of both ends. There are several possible answers to that:
First, because blocking one side is enough;-)
But the an explanation I prefer is to remind that STP cannot know that this link is a fiber going to a single neighbor bridge. This link could be connected to a hub, where on the top of the neighboring bridge there would be some hosts (PCs, routers etc...). To put it short, STP must provide connectivity to this link. That's why *every* link has a designated port that connects it to the root bridge.
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...