PVST vs Rapid STP | Cisco CCNA 200-301

[Music] [Music] [Music] there must be constant [Music] [Music] [Music] don't get out what you put all in the [Music] [Music] and welcome everybody to the live stream it's great to have you here it is CCNA Sunday I absolutely love doing these streams and taking requests today's topic regarding a rapid spanning tree versus the original crunchy flavor from Colonel Sanders the original I Triple E flavor of spanning tree that idea was brought to us by Gus so I appreciate it it's right on the blueprint for Cisco CCNA 200 301 and I'm happy to do it so without too much fanfare let's go ahead and go to a whiteboard and let's take a look at the original flavor the numbers for it rapid spanning tree and also identify what some of the differences are and then we can actually verify it in the lab so let's do that now um if we take a look at spanning tree there's a couple of things that we probably had a review just to make sure we're all on the same sheet of music and if you haven't yet seen the live stream on spanning tree we had a couple of them one with port fast and we had one with the basics of house betting free works and then we had yet another another another what I remember the topics specifically so we've had like three of them this is just one last add-on probably the last one for CCNA that we're gonna do but let's take a look at how spanning tree operates whether it's per vine spanning tree or rapid pantry and we'll get to those differences in just a moment uh spanning tree identifies let's go back to the camera spanning trees job in life is to say loops are bad now if you're a rollercoaster or you work for an amusement park like Six Flags Magic Mountain which has great rollercoaster loops are great but in a network we have a loop where a frame just keeps going around and around around not good see in an IP packet there's a header that in that header has a TTL field time to live and if a packet gets forwarded to a router that router decrements the TTL and eventually they'll say yeah you've been here too many times I'm going to go ahead and kill you because the TTL is zero that's by the way how traceroute works traceroute many places the TTL so that routers respond back but at layer two there's no there's no such TTL mechanism time to live at layer two so spending trees job is to identify parallel paths and then temporarily block on one of those ports so that we don't one or more ports whatever is required so we don't have a loop that's how it works and so in the case of rapid spanning tree or per VLAN spanning tree it does the same job it identifies basically does three things it identifies route ports well let's start with the beginning route switches which is like King Kong and then all the losers what do you mean Keith all the losers all the devices that were not the root bridge they are going to become non route bridges and they are going to identify route ports that's the port's that are going to be forwarding in the direction of the route and then they're going to decide on everything that's not a root port designated ports des IG does a I can type and talk at the same time no I can't designated ports and Disney imports our ports that are forwarding away from the root and the challenge is here you can only have one root port per switch that's it no more and you can only have one designated port per segment so a segment would be like this one right here and this one right here and this one right here and then so everywhere the connection you can have one designated port that's one switches forwarding on a on that on a segment so in the case of switch one let's let's actually do this let's pick an another switch so let's say switch three is gonna be the route we make it the route we give it a lower bridge a a higher priority which is a lower bridge ID we'll give it a better priority which is a lower a lower number making it the root bridge so all of this Forks would be designated because it's the root they would all be forwarding if this client had access if this switch had access ports and the VLAN we're focusing on the same VLAN 10 they would be designated also all designated and then these other switches if this was all the same ethernet speeds they would figure out okay great that's gonna be my root port based on the lowest cost so the rate the way they know cost is they know their local interface costs and they also know what's being advertised by the route routes and the route says this the cost to get to me is zero because I'm the route and so the in this case switch to and switch three they get that advertisement through be PDUs and they say okay my local interface port cost is 4 plus zero that you're advertising a cost of four and that's how they decide what their route port is going to be the one that has the least cost overall to forward in the direction of the route so switch one and switch oh here's the route sorry okay I was like where's the route all these guys are gonna be route ports and then on this segment and this segment where there's no route ports we have to figure out which one's going to be designated and so in this case between switch one and switch two and you know what I would love your input on that switch one switch two neither one of those ports are gonna be their route ports and there's only gonna be one designated port per segment so my question is who gets to be the designated port for this segment between switch 1 and switch 2 is it going to be switch one on port 1 slash 0 or is it going to be support switch to port 1/1 that's my question and there is I've discovered like 10 to 12 second delay for the stream to happen so I know that it's gonna take a moment for you to chat back but if you'd let me know and for bonus points you can also say why if you'd like that would be awesome so which of these two is going to be the designated port for that segment between switch one switch 2 and if you don't know yet that's cool if you're just joining me for the first time please feel free to subscribe there's a whole playlist for CCNA and if you go through those there's several of them on spanning tree so Wow okay Randall r-randy is the first one in there with a gig Oh No Murray awesome I'm fantastic so Murray and and Randy and Gus fantastic they're saying 1/0 this guy right here is give me the designated port for the segment and the and the duking it out was because switch 1 and switch two they both have the same cost to get to the root so that would be the first factor but they both have a cost of 4 or an equal cost to get to the root and so the next factor is the bridge ID and if the priorities were the same going down here to the base MAC addresses switch one has a lower base MAC address which would make him have a lower bridge ID which makes him win and so switch to says Oh bummer you can't have two designated ports on a single segment and it blocks and that same logic carries out for the rest of the network and we've covered that a few times so fantastic thanks for the input I want to make sure I remembered how that worked and now I do I appreciate your insight there now let me go ahead and clear that screen now that we've warmed up to this idea and let's take a look at rapid spanning tree versus the original crunchy flavor of spanning tree and the original flavor from the I Triple E is called and let me do over here I'll call it just STP and that the numbers for is 802 dot one D that's the standard 802 dot one is in don't you want to use something better than the original flavor of spanning tree but what we just described is how 802 dot one D works it is and then we have Cisco that made some enhancements to it and let's talk about some enhancements Cisco said do you know what it takes so long takes so long for a spanning tree to converge in fact list let's demonstrate that let's go down here to this switch right here switch 4 so on switch for I believe this is gonna be the root port and on 2/3 is can be blocking and if we don't use any enhancements no tweaks no enhancements from Cisco or no rapid pending 3 with traditional pantry if we stop this port or block it or turn off a 3/1 it's not gonna immediately switch over its sorry and the topology here switch 1 is gonna be the route by default and that's the topology we're starting with so that's why this is the part that's like hey keys we just made switch 3 the route if switch 3 was the route then this would be the root port 2/3 but the root is switch 1 by default because has a better base MAC address which makes for a better bridge ID so as a result this is give me the root port if this is the root port and we we turn off that port 2/3 takes a long time to figure out and go to the all the states before it's gonna start forwarding traffic on 2/3 so listen let's actually take a look at that with these two interfaces right here using the original 802 dot 1d ish I say ish with a little bit of humor there flavor of spanning tree so let's go ahead and clear that screen and let's go to the lab and actually take a look all right so we want to go to switch 4 let's just verify real quick this just pick one VLAN instead of all VLANs it's to show spanning tree for VLAN 10 okay so the the root port is gig 3/1 based on our diagram we just bring that up real quick again so there's 3/1 it's the root port and will notice that 2/3 is currently blocking and there it is so it's in a blocking state so if we were to do OH and we're running rapid spanning tree at the moment so rapid spanning tree converges a lot faster so I'm gonna use this really awesome tool you're gonna love it it's called notepad and it's gonna change this whole topology in like 10 seconds to go ahead and be the traditional flavor of spanning tree from a Cisco's perspective so we'll do config T and then we'll do a spanning tree mode P vs T which is how you spell the original flavor and Cisco and it does Purvi that's bang tree and then we'll just type an end and I'm going to copy and paste that across the whole topology and that way we can see how slow this thing is to converge so I just copied that to my buffer switch one done switch to done switch 3 done four done five done great now what we have here if we go back to switch 4 and we use that same command of show spanning tree for VLAN 10 now we have all these ports look at this poof here's the root port it's in listening state and this be a great time to talk about the States by the way so with traditional spanning tree and let me get a pen I'm just gonna annotate this as we we go through it together so 802 dot 1d the original flavor of spanning tree and we can also see it here this is how cisco hints that we are using the older version of spanning tree which is most like a torch at 1d we have some states that these ports can go through and these port states include well let's see here let's talk about list list yeah for States to be accurate so we have disabled officially and disabled means that spanning tree is not running on that port so we we don't see that too much because the port would be down not really running spanning tree we also have blocking which we can see well we can't see right here cuz we haven't converged yet when i refresh the screen we'll be able to see that we have listening and we have learning and we have forwarding so we can see a few of those right here so we see listening at the moment right here and we don't see learning because what happens is it's going to go from with traditional spanning tree there's this delay time right here the forward delay and what's gonna do it's gonna go from listening for that forward delay which is 15 seconds and then once it's figured out okay we're safe it then goes to learning for another 15 seconds based on this forward delay and then finally it goes to forwarding so if I was to go ahead and refresh the screen here for a moment and I'll use the up arrow key the reason a chuckle is because these line up with exactly where they were before there's just a fortunate stroke of luck but anyway now they've converged and now our root port is forwarding so forwarding right here and then we have a port that's currently blocking that's 2/3 and we are running I Triple E now in Cisco when we're running 802 that 1 D what we're really running is P vs T plus that stands for per VLAN spanning tree and it's it's not exactly like 8 or 2.1 d but it is very very compatible with it and one of the biggest difference is that with per VLAN spanning tree it has a separate instance for each and every instance of each and every VLAN so if we have 15 VLANs that means we're gonna bring running 15 instances of spanning tree one separate for each one so even though in our top which one is like the root for all of them by default we're gonna have if we have 200 VLANs we can have 200 instances of spending train then we can tweak and uniquely modify them we did that in our load balancing video regarding spanning tree so what else do I want to say about this okay so it's pervy lam and these are the states that the official 802 dot 1d can go through with spanning tree disabled blocking listening learning and forwarding oh also let's point this out too so if this is switch one and we've got our topology here so there's three down there and then switch to up here and then switch four and then one over here we have five I think we have a link here between the two also now if we have this topology and switch one is the route with the traditional and I when I would say traditional I'm talking from a Cisco perspective per VLAN spanning tree that's as traditional as we're gonna get what happens is the route is gonna generate a hello and hello message mom a bpdu that get OSPF on my brain it's gonna generate an bpdu every two seconds so the route gets to control that so if we change the hello time on the route to every three seconds or four seconds for six seconds the whole rest of that spanning tree topology would buy in they're all listening and getting these numbers here from the route and simply applying those but with traditional spanning tree what happens is this route when it burps that would be a good way to think of it when it spits out when it sends like like when it throws out this bpdu every two seconds all the other switches when they receive it so in this case we have switch one who sends it and that would be switched two and switch three that receive it that triggers them like I better propagate the bpdu down the rest out through my designated ports and it then takes the it that's the message for it to say okay you got the BPD from the route now you turn around and you add your own cost and all those details about if you're the designated port for downstream segments and you send it so it's like switch one sends a beep video and then the other switches oh send their bpdu and then the other switches send their BPD so everything is like a waterfall from the route as far as the BPD use that's the triggers little thing now in rapid spanning tree is different and rapid spanning tree every switch that's the designated switch for a segment is going to automatically every 2 seconds on their own timer gonna send out BP views and the benefit of that with rapid spanning tree is we can use those little B PDS as a holo-message as a as a timer so if I'm a switch and I'm running rapid spanning tree with another device on the same segment and I haven't seen hellos I will assume hey there's a problem and I don't have to just rely on the root triggering hello messages I can have that as an added bonus of knowing that there's a problem on the network that's just one of the the tiny changes with rapid spanning tree we'll talk about more here in just a second okay so that is rapid spanning that is per VLAN spanning tree the 802 that 1d let's take a look at the priorities by default on Cisco the default priority for the interfaces is 128 and if there's a tie breaker and this is switch for a switch for sends B PDUs down to switch 5 it's going to indicate its priority on these ports so these ports are 1/1 and I think it's 2/2 and so what it would do on 1/1 who say my priority here or my my priority is 128 and on this interface be 128 and if one of those was lower switch 5 would say okay the the cost on switch 4 is the same as far as determining a route port the port priority is the same and it's at that point when it would then take the the port number this value here or this being advertised so 1/1 would be advertising a 6 for the actual port ID and 2/2 would be advertising an 11 and that's why switch 5 would choose this port right here because it got advertised cost being equal bridge ID being equal port priority being equal the lowest port identifier was located on this port so over here on switch five that's port 3/3 okay so that's what this part is and the type this is also interesting there's two options here we have shared and point-to-point and all that's all that it's referring to is what kind of link am I connected to if you have real Hardware I'm using a similar virtualsystem and i hard-coded these I cheated a little bit but if you have if you're connected to a hub like half-duplex it's by default gonna show up as a shared connection and if you're you have full duplex it's gonna show up here as p2p and then you can hard code them any way you want them either way but that's the default so p2p or shared simply refers to the type of interface the duplex that's being used at that moment when that switch is brought up and this is hard-coded over here in this column we have a few options that can come up edge as we talked about in our port fast video edge simply means that port fast is enabled on this port which means that we're not gonna wait as long when that port comes up to go ahead and start being a designated port for it because there's nothing else out there it's it's gonna be safe there's none other switch not a possible loop and that's what this edge refers to I'll also show you here in a few moments that there's other messages that can show up here as well but that's what edge means so that is the traditional flavor of spanning tree and let me demonstrate how slow it is why it's so painful oh my gosh so let's go ahead and take out the route port which is 3/1 right here we'll just shut it down and then this other port 2/3 which should start forwarding it's just like just takes forever it's just like an eternity so let me go ahead and clear that off hide that screen and let's go ahead and do it so we'll do a config T interface gig 3/1 and before I shut down this port this be a good time to say your final goodbyes see you later see you later root port you did a great job and good luck on another port figuring out fairly quickly about becoming a root port because it's gonna take a long time with spanning tree ah ok here we go so we'll do a shot down and then we'll just use the up arrow command for a show spanning tree for VLAN 10 and you'll notice that 2/3 right here has now gone into listening States so just to recall where that is that's this portrayer and it's gonna be the new root port but holy schnikeys it's got to go through listening state first you know nobody's got time for that it's gonna take forever so it's got to go through listening and then that's gonna be for the forward delay time which is about 15 seconds well not about is 15 seconds and then after it goes through listening it'll go to learning meaning it's still not forwarding traffic but it's now learning layer 2 addresses that show up on that port and then finally it'll go to forwarding so hit the up-arrow key there's learning state meanwhile customers like off of switch 5 that needed to go through switch 4 they're in trouble I mean they just can't forward any traffic it's like doo doo doo doo doo - 30 seconds is long long time to wait for a network to reconverge and start forwarding so eventually if we there we go so now it's forwarding yay and that took a long time that's good spanning tree the traditional flavor has to go through listening and learning until it goes to forwarding now Cisco came up with some enhancements for this and one of the enhancements and this is also a part of our discussion is what are something enhancements that Cisco brought to the table with traditional spanning tree and one of them is called uplink fast uplink fast we can configure on a traditional spanning tree switch like switch for that says hey buddy you got a report but you know what I figured out beforehand that if that port goes down or isn't good go ahead and boom switch over to the other one that way you can get your another uplink you know going up faster and have it work a lot quit more quickly so that's what we used to do like a decade and a half ago to improve the performance as we'd use uplink fast on the non route switches and that way we could have that switch over quickly also if there's a failure indirectly in the network somewhere sometimes that takes a long time including going through blocking for 20 seconds then listening then learning which might take 50 seconds to actually converge for an indirect failure somewhere else in the network and so for that feature we had a feature called not for that improvement of that we had a feature called backbone fast and backbone fast you don't just put it on one switch like we did here with our switch for life with uplink fastest backbone fast you put it everywhere and it allows the switches to communicate better and take more aggressive action if there's it failure as opposed to just waiting the wait you know the block time and then starting to go through this thing and learning and then finally forwarding after you know an eternity 50 seconds he's like forever so those are some enhancements that Cisco incorporated are added so lysse uplink fast backbone fast now port fast is still good whether using rapid spanning tree or or the legacy one so that's important to use either when we've had a video separately on that and so what happened was the standards group I Triple E came up with a new flavor of spanning tree and what they did was they took a lot of those features that are baked into backbone fast and forefoot and backbone fast an uplink fast and they put them into rapid spanning tree and so without having to configure manually backbone fast or uplink fast we get a lot of those features just by using rapid spanning tree and it goes something like this so I'm going to bring this port back up yeah yeah just wash my hands and can't do a thing with them so I'm gonna bring this port back up interface gig let me take a look at my topology to make sure we're all together 3/1 yeah 3/1 let me bring it up so interface gig 3/1 will do a no shutdown let that come up and then I'm gonna use this really high-tech tool called notepad and what we're gonna do is we're gonna change the spanning tree from PBS T which is the most compatible with the Cisco's with the I Tripoli's 802 a 20 and we'll change it to rapid which it really is rapid spanning tree but it's also per VLAN so if you have a hundred VLANs you have a hundred separate instances but you get the benefit of rapid spanning tree so let's copy that and I'll just go to switch one and boom I'm just right-clicking to paste these in and then we'll give it a few moments to converge and a few changes a few a few differences well I let that settle for a moment here's a few differences with the rapid spanning tree above and beyond what we've already discussed one is that if we have a change in the network and I'll just say it topology change so if we have a topology change somewhere down here what used to happen is we'd forward that change in the direction that notification towards the route at our route ports it would hit the route and then the route would say Oh dip ology change and tell everybody else to go ahead and flush their MAC address tables and not keep anything longer than eight not keep anything it hasn't been seen as far as MAC addresses in the last 15 seconds well with the rapid spanning tree that topology change still happens we still send it but switch four says you know what I don't I don't I hear ya switch five I trust you you're you know you're unning rapid spanning tree with me I'm just gonna go ahead and start acting on that now I don't need to forward them all the way up to the root and then wait for the root to send me a message for ad apology change I'm gonna just go ahead and do it so the topology change happens a little bit differently it still works I mean the end result is the same it's just more efficient also if these are p2p links full duplex they are going to negotiate with each other and they can have agreements and proposals that can help them identify including hellos that are being sent every two seconds and they can have they can identify more quickly that there's been a topology change also if this is the route port on switch for R P there we go if that's the report and this is a a block port instead of having to wait the entire time before we converge with rapid spanning tree if this port goes down this port automagically kicks into gear says okay I'm becoming the root port he's that whole thing about you know waiting and learning anything else I'm just gonna go for it and that makes convergence a lot faster so in that light let's talk about these stages or the the states in rapid spanning tree and they are right here last night I thought you know I got some feedback great feedback from one of the one of the participants in our channel and they said regarding this topic that you taught it would have been better if he just made a little chart and then worked off that chart and that way it would have been more concise and I thought oh ouch and I thought he's right and so I'm always interested in feedback because everything I get feedback wise I can look at and if I'm not aware of something I can't really fix it so I think I'm grateful for that feedback and that's why last night after Gus recommended this yesterday in a live stream I made this table I checked it a couple times hopefully it's accurate I believe it is and we'll go through it right now to make sure we I see the states and how they work so in traditional spanning tree as far as states go over here on the right hand side here as far as states go we'd have disabled blocking listening learning forwarding great and we looked at some of those in 802 dot one W which is the the I Triple E term for rapid spanning tree and the way I remember that if it's important is like Bugs Bunny so with Bugs Bunny there was Elmer Fudd I'm hunting wabbits and so whatever this is like twenty years of me eighteen years ago somebody mentioned yeah that's how I remember rabbits rapid spanning tree I'm running rapid spanning tree 802 that one W it's hard to forget after that so that's I passed that gift on so eight or to that one double use rapid spanning tree and here are their states we have discarding discarding discarding so there is no listening state and then we have a learning state and then forwarding so basically they said you know if the traffic if a port is not forwarding traffic says rapid spanning tree let's just refer to it as discarding meaning if it gets a frame in it's not gonna forward it it's not gonna process it and let's just go ahead and call it discarding so officially that's what it's called so here the eighth or tenth one D States for a port here are the 802 one W so this is the traditional flavor STP this is rapid and now now comes the interesting part of the show where we talk about what a Cisco shows you if you're running either the per VLAN spanning tree or rapid spanning tree it will never show you block I ran I'm sorry you'll never show you discarding if you look at the output which we will here and we just did a few months ago if we're running the Purvi that spanning tree it'll show block or listening or learning which we've just witnessed a couple of those or forwarding but it will never see discarding even if you're running spanning tree so if you enabled rapid spanning tree it'll still just show blocking learning or forwarding as far as these states that's like the current operational procedure for that interface so that was you know when I first learned about rapid spanning tree and I thought oh right I'm running rapid spanning tree and then I still saw it's a block I thought what what what the heck why is it still say block I'm running rapid spanning tree it's just the implementation on a Cisco device that they chose to use some terms like blocking instead of discarding regardless if you're running the 802 2.1 D which is the per VLAN spanning tree or rapid per VLAN spanning tree the output for blocking versus discarding is shown as blocking 100% of time so that's good to know because you'll never see the other one the other thing that they did was with a torch at 1d and I say they'll talk about the standard first and we'll talk about Cisco another thing that happened was there's various roles which we discussed earlier so in 802 it 1d we have a root I'm talking about port roles so ports that are facing or forwarding towards the root are gonna be route ports assuming switch 1 is the root bridge fantastic and then ports that are forwarding away from the root are going to be referred to as designated ports great no problem there either and so on this segment here between switch 2 and switch 3 they're going to Duke it out if they have equal cost then the one that has the lowest bridge ID gets to be just a dusty in port and the other one gets to go ahead and be blocking so that's fine that's great and in 802 dot 1w rapid spanning tree they also have root and designated which is the same process but they also took ports that are currently blocking or in their terminology discarding and they gave them additional roles now what's the benefit of having additional of roles well a moment ago we just saw that we had a root port here that was forwarding on 3/1 we took and then this port was blocking and then with traditional spanning tree when we shut down 3/1 how long did that take it was at least 30 seconds and in a hardware based environment it should be 30 seconds listening learning and then finally forwarding and that's a long time so what they did what with rapid spanning tree is instead of just saying this is blocking they are going to load it up or predict that this is an alternate port meaning it could be an alternate when I see alternate I want you to think alternate route port because that's really what it means so 2/3 is an alternate route port it's like it's like having a in baseball shoes baseball analogy it's like having the the guy who's gonna bat that and he's up he's gonna bat he ready to go and then if something happens they're gonna back him up with somebody to come in and bat for him now instead of taking at a baseball game which may be moved slow I don't know but I was at baseball sometimes does move pretty slow if you're a huge baseball fan I get it that's fine but if it took like an hour for the primary battered say oh I'm not gonna bat and they're gonna replace me took an hour it's like why wait just put the other guy in before hands think about who's gonna be the replacement and put them in same thing here with the this alternate port if we have a route port and we have another one where we're seeing BP views that are coming in from the route or from that direction why not have that guy in the wings ready and if that route port goes away boom that alternate part can then immediately be transitioned into a route port and forwarded this the same benefit that uplink fast gave us with traditional spanning tree but it's baked in to rapid spanning tree so what I suggest we do is let's test it we are running rapid spanning tree now I just applied that to all of our devices and on switch for we can very easily shut down this port and then take a look at 2/3 and see how fast it comes up and in spanning tree with rapid spanning tree that is going to be 2/3 before we shut down 3 plus 1 2/3 is going to be an alternate port and it'll be labeled that way so let's take a look so I'm gonna hide that for a moment bring up my apology and let's do it so go back to the right switch that's a really good thing to do oh look at that well I was making the changes it had a little bit of grief let's just do a show interface trunk make sure my trunks are okay yeah my trunks are all all functioning that works all right and let's go to config T inter ends to it let's do a show first show spanning tree for VLAN 10 all right so VLAN 10 currently my root port is 3/1 looking at our topology make sure all here that's 3/1 right here it's our report and 2/3 check this out 2/3 says it is in blocking state not discarding but that's the way cisco shows it and it shows here as an alternate meaning that this port 2/3 is ready to go I mean if you if 3 1 goes away if the primary batter goes away I'm it I'm your next report and I don't have to wait forever to get there says rapid spanning tree because it's baked into the code so let's go ahead and demonstrate that interface gig 3/1 and we'll do a shutdown just verifying my port real quick and then I do show spanning tree or VLAN 10 and look at that bad boy that's our alternate port immediate well virtually immediately converged over to a forwarding port a root port and now we have connectivity once again where instead of having to wait 30 seconds it didn't even go through the learning state it's just said ok I'm in I'm ready to go and that's one of the benefits of the baked in features of rapid spanning tree it indeed is a faster for that reason alone for a direct network failure or interface going down the alternate port can come back up and take over so if we go back to this let's let's confirm a couple things and let me bring up my pen and let me clear that off so the roles here if we're running Cisco rapid spanning tree that which is really rapid / via than spanning tree we have roles of root designated alternate so 2/3 a moment ago was an alternate port and now it's a route port and then we also have backup which we'll talk about here in a moment but let me point something out when we were looking at this earlier I'd switched four and we were running the per VLAN spanning tree it also showed us alternate port and that when I was first learning spanning tree and implementing Cisco I was like wait a sec I was running per VLAN spanning tree before I was not running rapid spanning tree and yet it's still showing up as an alternate port that is the way that cisco has implemented it so whether you're running per VLAN spanning tree the original flavor or you're running rapid spanning tree if you have a port that could be a alternate port it's gonna be labeled meaning another port to the route towards the route that's can be labeled alternate and if you're running the traditional flavor of spanning tree it's gonna take a long time to converge even though it says alternate and if you are running rapid spanning tree it relabeled alternate and it'll be a lot faster so if we're an uplink fast in addition to the original flavor of spanning tree then it would converge and flip over much quicker but I wanted to point that out because like well this alternate row role Keith it doesn't even exist in the original spanning tree but yeah I see it here on my interface why is that and it's the implementation of Cisco and also very likely because they have some enhancements that can be added like uplink fast which is which actually help describe what that port is and why it does that all right the other element here that I'd like to shout about that could be a little confusing for someone you're looking at the output of show spanning tree is this right here and that is the the backup interface so NATO 2.1 d there's no concept of a backup well in the original I Triple E spec tree it isn't and in rapid spanning tree there's an option called backup and it goes something like this let's imagine we have two switches so we have switch a and switch B right there and let's imagine a is the route and we'll also say there's some connectivity there and we could have lots of connectivity because spanning trees gonna figure that out also I have a video did on ether channel so if you want to take a whole bunch of links directly between two switches and not have all of them but one be used you can create an ether channel anythin link aggregation protocol lag an ether channel trunk a trunk of ether Tennessee here you can create that you can use ether channel whether using trunking or not and go ahead and have those treated like one logical link from span tree so check out that video if you have never seen that but the point down here is what if switch be so is connected to and I'm gonna say a hub now if you're familiar with hubs hubs are a layer one construct meaning they have no idea about layer 2 addresses they don't know about layer 2 addresses they don't care about layer 2 addresses or anything higher basically bits that are spit into the hub are simply repeated back out on every other port so in this scenario well router to switch switch be because switch a is the route and there's nothing yet there's no switch is down here there's the possibility of this router break the switch being a designated port on this port and also on this port but check it out if it says B PDUs down both links it's gonna see the B PDS on the other side and so you can't have two designated ports on the same segment even if it's the same switch the rules for spanning tree says there's only can be one and so what will happen is that there will be blocking on one of these let's say this one and because this is a port that could be a designated port in case the other one fails that is referred to as a backup port so its role in 802 dot 1w which show literally as back meaning it's a backup designated port so the key is if it says alternate it could be an alternate route port and it says backup it could be a backup designated port going away from this from the route and I thought to myself how do we demonstrate that I always love to show you how you know what that looks like in the interface and so I came up with an idea and here it is what we could do is we could go ahead and turn off spanning-tree on switch five just for VLAN 10 now in a production environment you don't want to disable spanning tree but in this lab environment I'm gonna disable suspending tree for VLAN 10 no span and what will happen is switch 4 as he's sitting be PDUs out these two designated ports if I turn off spanning tree he'll basically see his other B PDUs coming back because switch 5 is not doing any kind of blocking whatsoever so let me turn off spanning tree I think that'll cause it for if it doesn't we'll tweak it but if I disable spanning tree from you then 10 on switch 5 these two designated ports will be able to see each other's content for the same VLAN yeah that's exactly right so I just think it's true I'm just thinking that through here for a moment so if switch 4 sends BPD's for all the VLANs and we just disable VLAN 10 for VLAN 10 only it would be able to see each other's BPD's because switch 5 is not disabling a parallel path and then we'll be out we'll be able to see switch 4 on one of those ports become a backup meaning a backup designated port all right so that's my theory I think it'll work and let's try it so let me go ahead and go back to our lab which is right there so let's just do a quick check oh let me let me heal like correct switch 4 is root port real quick interface gig that was 3/1 no shut down the show spanning tree for peel am 10 great all right so 3/1 ok he just ready came up so 3/1 because of rapid spanning tree is now the report didn't have to wait a long time for that also up here it's showing us that we're running per VLAN rapid spanning tree hence the RSTP there give me one separate instance for every single VLAN that's running so on switch five let's go to configuration mode and say no spanning tree VLAN 10 all right and this just do a confirmation show spanning tree for a VLAN 1 yep still running great great great show spanning tree over than 10 yeah not running all right so what we just caused to have happen is that on switch for just a moment ago it's two ports let's take a look which are ports 1 1 & 2 2 they were both designated let's verify that so here is 1 1 designated forwarding for VLAN 10 and 2 2 why was it blocking hold on a second oh did I just run this command mm-hmm okay just because I want to be darn sure when I ran that command let's just turn the spanning tree on for a moment it's paying sure you feel an 10:00 show spanning tree down 10 okay so spanning tree is running fantastic let's go back to switch 4 oh it's 1 1 and why is he blocking I'm really curious why is he blocking let's take a look at my porch real quick 1 1 & 2 2 this is switch 5 huh I am honestly expecting 1 1 & 2 2 to both beat forwarding because switch 4 has a better cost than whatever is out here at switch 5 let's go take another look okay now it's got me curious let's do this Oh and now it's going through okay all right so it's going through learning which is part of rapid spanning tree there's no listening state but there's learning and so we'll give this just a moment to converge I must have didn't think I did but maybe I I turned disabled spanning tree from Elan town switch 5 first and then did the show command because these two ports they should be designated ports so I just want to validate that first okay great gig 1 welcome to my world it's like wait Wow why is that that's that's a good way of learning by the way when you do something and then the responses the results don't match what you're expecting it's a fantastic opportunity to dive in and investigate which is what we just did alright so gig 1 1 & 2 2 on switch for are both in a forwarding state their role is both designated and what we'll do now is we'll go tip the scales on switch 5 by going into configuration mode and saying no spanning tree for VLAN 10 all right so now that we've done this if we go back to switch for switch 4 is now seeing his own BPD use between gig 1 1 & 2 2 and what I'm expecting if we do a show me then there we go thank you so now gig 2 to is shown as a backup port a backup port would mean an alternate non ultra either wrong work a backup port means another port that could be used as a designated port for the segment if the prior one goes away so if we went to gig 1 and we told gig 1 1 to shut down then 2 2 would flip over and become a designated port because it's a backup it's ready to go in fact we can test that real quick and erase gig 1/1 shut down we'll do a show spanning tree for VLAN 10 you know wait for just a moment for that porch really go down all right there's 2 - don't make me wait all right now it's designate I was still blocking holy cow a sec here wow it is going is that the right port yeah it is dang is good so 2 2 is going through it states of listening and not listening but learning because there is no listening state inside of rapid spanning tree but in a moment it will converge I would would have hoped it would've been a little faster but it's on its way yeah there it is in learning and eventually the good forwarding so I'm going to go out and bring back gig 1 1 that's just to make sure I'm in the right interface and then when gig 1 1 comes back it should be here in a moment so we've got this interface right here the gig - - which is now back up again gig when one is still blocking but it'll be forwarding here in just a moment great demo Caitlin how fast rapid spanning tree is yeah this is a simulated environment - so but for the uplink part it is rocket fast and for this it looks like it's just going to take its merry time ok so now it's in learning and eventually it'll be forwarding me I mean while bob is not able to Bob it Bob the customer at that network is not able to forward all right let's see if we've covered everything I wanted to cover as far as topics here have a little cheat sheet of notes and let me take a look and I wanted to address some of the features of rapid spanning tree and that is that these additional roles of alternate and backup and even if you're running the old flavor of spanning tree or the newer flavor of spank rapid pantry it still shows those roles either way so if you're running the traditional flavor and you see these roles just realize hey it that Sal Cisco's implemented it as far as the states go we have left states with rapid spanning tree so that we don't have a learning anymore with rapid spanning tree we just have I'm sorry we don't listening anywhere we said learning but what happens is that the actual formal term for a pork that's not forwarding traffic that is doing what used to be called blocking is called discarding but in Cisco will always see that with Purvi than spending for your rapid pantry will see that as block so those are important aspects hello messages are sent from the root every two seconds and every device running spanning tree on its desi imports will send hellos every two seconds as a keepalive mechanism to help identify failures faster in the network and see if I had anything else we've also talked about the yeah the the roles and the states as well that's what I wanted to focus on in this video was to take a look at those specific elements and this is all because of Russ's request which is straight out of the CCNA 200 301 by the way let me see if there's anything else that I wanted to mention back at the interface I think that's the thing that we covered most of it back at the interface of the lab we are running rapid pantry if we what oh if we had one other thing here if if our switch 5 was for whatever reason running a different version of spanning tree such as spanning tree mode and this is way you change the mode by the way let's go ahead and do P vs T which is the more original flavor we're gonna see in just a few moments is that because switch 5 is running traditional spanning tree or I should say more traditional which is per VLAN spanning tree and switch for it's running rapid switch 4 is going to identify the difference in the BPD is because they're slightly different and as a result it's going to negate or downgrade itself logically as it interacts with switch 5 so we should see here on switch 4 it should show that it knows about switch 5 being like a legacy STP device and let's bring up the lab and verify that so here on switch 5 if we do a show spanning tree for a VLAN 1000 it's still disabled I thought I enabled that let me let me go back and put him back to normal sorry about that I'm the spanning tree not running on switch 5 4 than 10 so spanning tree VLAN 10 all right Becky goes that takes just a moment so that's why if we got if this come in here show spank tree for VLAN 10 here we go so if we wasn't running spending for you wouldn't see these messages and they were that's why I wanted to point out so see how it shows the peer is running STP that's how you know that this witch is running rapid spanning tree or also MST multiple spanning tree actually uses rapid spanning tree behind the scenes and off of these two ports gig 1 1 & 2 to our peer is not and that's why these show up as STP so I'm gonna play back to this video and they oh yeah I forgot to bring that up or forgot to show that but a great opportunity to practice and learn which is what this is all about alright also because they enable spanning tree this should no longer show up in a moment as a backup port because there won't be there won't be parallel paths into the same Network segment so if we give that a moment yeah so right there it's no longer gonna be a backup port because it's no longer being seen on the other interface because spanning tree at switch 5 is blocking on one of those ports and as a result isn't propagating those frames through ok so that part is working like I thought it right all right let's do this I absolutely enjoy chatting with you I enjoy doing these live streams yesterday we did a live stream on subnet Saturday it was on the finger game and I watched the video after I I thought was great I trimmed it the back end so here's way in the live string and the live streams we do a pause a formal clothes then we come back and do QA so for those people who are in the live stream it's just for you just for us where you can chat and talk and then I clip those before on YouTube I clip them using their editor and then it clips off that back Q&A so it's just the the video on the live stream content and that's it and that's an extra bonus for people who show up for the live stream which I'm grateful yesterday I did a little clipping as I've done before like 30 or 40 times begin the live streams and it is stuck if I go to youtube studio it shows the video as check back later are still being processed so it's been over a day now almost 24 well not quite 24 hours so I'm checking with YouTube on that if after a week it doesn't like break out and fit finish I will re-record just in the studio here the finger game so I can insert it as part of the subnet Saturday playlist so you can have a complete picture so I probably will wait till like Friday and if it doesn't get cleaned up by then or available by then I was just recreate the short version of it and put it here in the playlist so thanks for that feedback I wouldn't have known that it was no longer playing if I hadn't had people let me know so I appreciate that okay so we have another stream on Wednesday I will announce that topic on social coming up I'll put it as part of the master playlist as well so for every who wants to stick around for QA and a little Keith unplug chat please feel free to do so I appreciate all of you joining me for the streams I'm having a lot of fun and I wish you the best of success in your career or your growth in CCNA or if you're past that you're helping this channel by coming back and saying yes I understand these basic concepts and I want to help answer questions for other people that my friend is fantastic so stick around for the Q&A otherwise we'll see a trails in the next video or livestream here on Keith Barker networking at you do thanks everybody [Music] don't get out what you put

Channel: Keith Barker

Views: 26,344

Rating: 4.9571867 out of 5

Keywords: 200-301, 200-301 ccna, 200-301 cisco, 200-301 vs 200-125, 200-301 cisco certified network associate (ccna), 200-301 videos, 200-301 exam, 200-301 ccna certification, 200-301 study, 200-301 cisco certified network assoicate (ccna), spanning tree, per vlan spanning tree protocol, per vlan spanning tree configuration, rapid per vlan spanning tree, per vlan spanning tree, cisco, ccna, stp, vlan, networking, cisco ccna 200-301, cisco ccna certification, cisco ccna training

Id: AzX3Nx0qVKU

Length: 57min 51sec (3471 seconds)

Published: Sun Feb 16 2020