All right, we made it through this very quick section and we're going back by the way very quick section. So let's just go over very quickly what we actually talked about now, we will review on how switches work right that they they learn source MAC addresses and they don't have it in their MAC address table they flood the network by looking right are looking for this particular market address market this MAC address okay. So go ahead and you know, started learning it and put it in in the MAC address table alright. And we talked about that spanning tree is purpose is to prevent switching loops. Again, if you have no redundant links, then spanning trees are really not doing it. Right.
But if you have redundant links spanning tree We'll go ahead and block a particular port to stop forwarding messages now that will stop it from listening will stop it from 40. Right. And we actually looked at the original, you know, 8021 d. SDP, which the latest version was back in 2004. So that's why there are newer ones now like CST over 8021 Q, and we have PVC and PBS t plus. Right and the differences between those are just CST which is a common spanning tree just uses one version or one instance I should say one instance or spanning tree across all your VLANs which is nice is your configuration, nice to handle but it does take up a lot of load on your CPU, and you may run into certain issues that we spoke of, as far as low balancing okay with people VST we can have multiple instances.
Okay? That means now we can load balance or send information one way and send information to other VLANs. What have you. And then PVC plus is compatible with all. And we talked about hopefully we learned already about the election process. Right, that bridge ID, that bridge ID, that is two things right?
Your bridge party number, which by default is 32 769. And then you have the MAC address those two numbers make up your bridge ID. That's what spanning tree looks at lowest root bridge. Highest is a switch, I guess, say hey, you're it we're going to block a port on you. How based on bandwidth or is it facing the root bridge or not or highest MAC address? highest MAC address.
Okay. Remember if asked Pato Cisco did tournament, which way information should go? Or should or portion be blocked by using the highest cost path? Okay, remember that triangle, say, Oh, well there's just 19 going to bridge. This is 1919 is 38. That means let's got Bigger, Longer, slower, further.
So I was going to block that particular port. Okay? But again, easy way to look at it is all ports facing the root bridge our reports they will never be blocked, okay, they'll never be blocked. Alright, so that's it. We're done here. So on the next section, we'll actually start configuring spanning tree in different scenarios.
I'll see you then.