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This Cisco video training with Jeremy Cioara covers troubleshooting Cisco networks, including topics such as IOS tools, VLANs and spanning trees, router performance issues, and more....
This Cisco video training with Jeremy Cioara covers troubleshooting Cisco networks, including topics such as IOS tools, VLANs and spanning trees, router performance issues, and more.

Related area of expertise:
  • Cisco networking level 2

Are you ready to run a Cisco network?  You will be, once you pass your TSHOOT exam. TSHOOT is the final step for earning Cisco's CCNP certification.  Employers trust that CCNP certified staff have the vital, problem-solving skills their network needs.

With tech guru Jeremy Cioara in the virtual chair next to you, you'll get the training you need super-fast, and you'll love every minute of it!  His TSHOOT video course is 80-90% hands-on, and Jeremy's filled it with tons of unscripted, real-world troubleshooting demonstrations.

By the time you're done watching, you'll be ready for the TSHOOT exam and actively troubleshooting your own network.
1. TSHOOT: Setting Your Expectations (16 min)
2. General TSHOOT: The Troubleshooting State of Mind (28 min)
3. General TSHOOT: Troubleshooting Before You're Treading Water - Proactive Steps (18 min)
4. General TSHOOT: Troubleshooting Before You're Treading Water - Proactive Steps, Part 2 (39 min)
5. General TSHOOT: IOS Tools to Monitor and Maintain the Network (27 min)
6. General TSHOOT: IOS Tools to Monitor and Maintain the Network, Part 2 (56 min)
7. Switch TSHOOT: VLANs and Spanning Tree Concept Review (19 min)
8. Switch TSHOOT: VLANs and Spanning Tree (30 min)
9. Switch TSHOOT: VLANs and Spanning Tree, Part 2 (28 min)
10. Switch TSHOOT: L3 Switching and Redundancy Protocols Concept Review (21 min)
11. Switch TSHOOT: L3 Switching and Redundancy Protocols (36 min)
12. Switch TSHOOT: L3 Switching and Redundancy Protocols, Part 2 (27 min)
13. Route TSHOOT: L3 Connectivity and EIGRP Concept Review (23 min)
14. Route TSHOOT: L3 Connectivity and EIGRP (48 min)
15. Route TSHOOT: L3 Connectivity and EIGRP, Part 2 (37 min)
16. Route TSHOOT: L3 Connectivity and EIGRP, Part 3 (19 min)
17. Route TSHOOT: OSPF and Route Redistribution Concept Review (23 min)
18. Route TSHOOT: OSPF and Route Redistribution (41 min)
19. Route TSHOOT: OSPF and Route Redistribution, Part 2 (29 min)
20. Route TSHOOT: BGP Concept Review (18 min)
21. Route TSHOOT: BGP (26 min)
22. Route TSHOOT: Router Performance Issues Concept Review (28 min)
23. Route TSHOOT: Router Performance Issues (43 min)
24. Security TSHOOT: Access List Concept Review (17 min)
25. Security TSHOOT: Access List Chaos (62 min)
26. IPv6 TSHOOT: IPv6 and IPv6 Routing Protocols (21 min)

TSHOOT: Setting Your Expectations

General TSHOOT: The Troubleshooting State of Mind

General TSHOOT: Troubleshooting Before You're Treading Water - Proactive Steps

General TSHOOT: Troubleshooting Before You're Treading Water - Proactive Steps, Part 2

General TSHOOT: IOS Tools to Monitor and Maintain the Network

General TSHOOT: IOS Tools to Monitor and Maintain the Network, Part 2

Switch TSHOOT: VLANs and Spanning Tree Concept Review

Switch TSHOOT: VLANs and Spanning Tree

Switch TSHOOT: VLANs and Spanning Tree, Part 2

Switch TSHOOT: L3 Switching and Redundancy Protocols Concept Review

Switch TSHOOT: L3 Switching and Redundancy Protocols

Switch TSHOOT: L3 Switching and Redundancy Protocols, Part 2

Route TSHOOT: L3 Connectivity and EIGRP Concept Review

Route TSHOOT: L3 Connectivity and EIGRP

Route TSHOOT: L3 Connectivity and EIGRP, Part 2

Route TSHOOT: L3 Connectivity and EIGRP, Part 3

Route TSHOOT: OSPF and Route Redistribution Concept Review

Route TSHOOT: OSPF and Route Redistribution

Route TSHOOT: OSPF and Route Redistribution, Part 2

Route TSHOOT: BGP Concept Review

00:00:00

Well, it's time to visit our final routing protocol, the big grizzly protocol so known as BGP. BGP is awesome. It's one of those protocols you can never reach the end up. So what I want to do in this section is again get our blood flowing before we get into troubleshooting. Look at just kind of a big picture

00:00:18

concepts of BGP and then some key troubleshooting tips. All right, well let's start off with the place of BGP and it's not always where everybody expects. Now you're at the end of your CCMP journey so you have a pretty good idea of what BGP is, I'm assuming, which it is the routing protocol of the internet.

00:00:37

ISP is everywhere, exchange their internet routing tables using BGP but you also know that BGP is one of the slowest routing protocols on the planet by design. It's in, it's funny when talking to CCNA's people, people are just getting into the networking, you bring up BGP and they go, "Oh what's that." You go, "Oh,

00:00:55

it's a routing protocol of the internet." And immediately their mind goes, "Wow, that must be really good, really fast, really", I mean like all of these preconceived notions because of course, the internet is so big you have to have a really crazy big protocol to run it, which it is true. BGP is crazy big, no doubt. But

00:01:13

it is not fast but it's really slow by design because when you have a network the size of the internet, you can have rapid fire updates that go across the internet and tie a network goes up and down. So, it's not the ideal protocol for internal use. It's

00:01:29

meant for external use. Now BGP is typically used between internet service providers but larger companies or companies that deal with multiple internet service providers find BGP very handy to allow themselves to advertise their own block of addresses. So maybe this company

00:01:47

right here hosts a website or has an email server or whatever. They want something that's available through multiple service providers. Here's ISP1 and ISP2. Well, outbound access is easy. All you have to do is setup a default route and you could say, okay well, this is we'll say the preferred, you know, my primary path and this is my backup.

00:02:09

Or you can even set up if you got equal cost internet connections or equal internet connections, you can set it up to where it'll load balance between those out bound without a problem. It's the inbound stuff that gets pretty complex and harry, because you got, we'll say, let's just say that 12.1.0.0 sub net.

00:02:30

You're advertising out to the world. Well, when you advertise that out to both ISPs you're going to get traffic that comes in, it's low balance between, you know, those kind of but not really you have to tweak how the distance of this and you have to make sure that this address block is independent meaning neither ISP is claiming it for themselves like they're the owner of those so you have independent address spaces. There's a lot of complexity

00:02:55

that deals with having your own address space and handling redundancy with BGP but that's one of the uses of BGP. But let me broaden your mind a little bit because larger organizations uses BGP for not just internet connectivity. I just, I was just dealing

00:03:10

with the whole network team from a, I'll just say a credit services group. It's a well known credit card company. If I said the name, you would recognize it and I was talking with their group and I say, "Well, how are you using your network? How was your network designed?" And they said, well internally it's just a bluff, I mean we've got OSPF running internally. We've got the EIGRP

00:03:33

between another group. We're redistributing between those guys and he said, we even have RIP in some areas of the network because some of our mainframe systems only support the RIP protocols. He said, we have every routing protocol under the sun but we also use BGP, not just for internet connectivity. They use BGP

00:03:51

to the internet but they also have partner organizations. I'll just put partner A over here which might be a credit processing firm, partner B which might be another credit card company I said B but I wrote A so we've got all these partners and so what they wanted is they wanted to be able to hand out routes to those companies and accept routes from those companies within controlled limits. BGP allows you to do that. So, one of the only routing

00:04:18

protocols that does not trust neighbors. You actually have to manually configure your neighbors and then you can put very very tight filters on exactly what route you send your neighbors and what routes you accept from them. So BGP is awesome when it deals

00:04:35

with controlling what routes you're allowing inside and outside of your company. All these other protocols, OSPF, EIGRP and RIP they're super, well except RIP. They're super for internal route exchange because everybody is trusted, everybody just exchanges route and it just works internally by default but when you really want control, that's where BGP comes in. Okay.

00:04:56

So let's roll down into the facts about BGP. BGP is one of the, well, it's the only internal thing, I think-- I think it's the only protocol that runs, routing protocol that runs on top of TCP. All the other protocols, OSPF, EIGRP, RIP RIP uses UDP. EIGRP and OSPF have

00:05:18

their own little reliability mechanism. They are their own protocol. They don't use TCP or UDP. So BGP being that it's slow and clunky, when you really get down to it, it's a let's go and use TCP three way handshakes, we'll use TCP keepalives as kind of our hello message, if you will. So it really relies on TCP to ensure the

00:05:38

underlying network fabric is working okay between the BGP neighbors. So TCP is one of the core pieces of BGP. Updates, of course are incremental and triggered. It would just be madness if BGP would send an update anytime a change occurred because in a routing table the size of the internet, you're always seeing routes goes up and down, up and down and all kinds, I mean a hundred of changes to the table happen every instance. So in

00:06:06

BGP we're going to say, oh, oh, let me send that, right away. Okay. Let me get that. It would just bug the whole thing down and thus this talks about why BGP is so slow. It is because it's impossible to have rapid fire triggered updates, it's just going to go ahead and receive all the updates and whenever it reaches its increment, then it will send all the updates at once to its neighbors and I kind of describe it like you know, a router receives an update and say, "Oh thanks for that. It's nice. Let me just

00:06:35

kind of sit on that for a little while. Oh, here's another. Okay. Let me sit on that." And then once it reaches its timer, it says, "Okay, well let me tell this to all of my neighbors. And so it's often used DNS as a good comparison you know, where you add in a DNS entry to an internet name server and then it replicates to its DNS peer on a time interval. So it takes a long time

00:06:56

for a route domain name to show up in the internet DNSS, a kind of same style of concept with BGP but maybe not quite as long. So you're probably looking at that forth bottom bullet, I'm not even going to go there. Guys, I was like, do I go to the metric

00:07:13

of BGP and I thought, no way. Shoot on back to the route series in the CCNP, meaning, you might remember that, that list, I think it's about 10, 11 different I think it's 10 attributes that BGP uses to figure out the best way around the network where it says, "Okay, what's the highest weight?" Figures that out on the space on it. Okay, let me check the local preference and it just keeps

00:07:35

going down to this list. The big tie breaker that most of the time breaks the tie is the autonomous system path which is why BGP by default is no better than RIP in many senses because you've got you're autonomous systems right here. Will say it's AS, just

00:07:50

say 100 connecting to this guy and this guy, this guy and all these autonomous systems all around the internet and you're trying to find the best way to get to this autonomous system up here. By default most of the metrics ties to the BGP says, "Well, I can go through this autonomous system, two, three, and I'm there or I go, okay, one, two, three and eight, well, of course my diagram would be a tie." But you get the idea. It uses autonomous

00:08:18

systems like hops and finds his way around the network that way, which is just kind of a random roll of the dice. So that's one of your big jobs when you get BGP as tweaking the metric for the routes that really matter. So you make sure you uses the best exit point. So and I mentioned this, it is the slowest routing

00:08:35

protocol in the planet to converge by design. As we get ready to dive in to the troubleshooting and so my key tips for you when you do trouble shooting, let's look at the packets and tables that build BGP, kind of behind the scene, what does it use. Well, it's nice because BGP despite its massive

00:08:55

scope and complexity when you get to the route maps and modifying your attributes of BGP and your metrics, really it's simple when it comes to the communication. You've got four types of packets that it sends. You've got yours open which says, "Okay, I want

00:09:11

to start this session." Now keep in mind all of these, I'm just skipping the right by TCP, all right. TCP does its thing. You got the scene, the scene act, the act where negotiating our session. So assuming TCP does its thing, the next packet that's going to come would be an open message. And the open message is going

00:09:27

to say, "Hey Bud, I'm BGP, let's be neighbors. I'm configured to talk to you, let's talk." So it's going to come back from the, well I should say the neighbors is going to receive that open messages and say, well, okay let's see if all of the criteria match? Am I configured to speak to you as a neighbor? Do I have EBGP multi app?" All of the configuration settings that BGP is required to do is compared in that open message. Assuming all

00:09:56

of those agree, they become neighbor. And then from there, they are going to start sending update messages to each other. "Hey, I know about this, I know about this, let's exchange our BGP tables." All of that exchange happens, life is good, from there on now all that's going to be sent is keepalives, but just duh! That's TCP keepalive, it keeps the session alive. Make sure that

00:10:17

the neighbor stays online. So if TCP fails, then your neighbor fails and then on that triggered interval, whatever interval you decide to set, it's going to send updates so that would be you know, anytime something changes in the BGP routing table. You don't want to see notification messages.

00:10:36

That's usually you think, well what kind of notification? You know that's just a message. It's like notification that means something bad happened. So you know, something maybe you tore down a neighbor, you shut down your neighbor, something like that. It's going to send a notification and just letting the

00:10:50

other guy know, "Hey, I'm going down, go ahead and tear down the session, TCP is limited and all that. Now obviously, if you lose network connectivity you're not going to get notifications. TCP is just going to die eventually, the keepalives fail and then by the time it's said and done, you will, I hate that when that happens. You ever heard that happen? You're just going

00:11:12

going and all this in your brain is like, I'm thinking about the Easter bunny. Actually I know why it happened. I've got, my Easter is right around the corner for us and my Aunt bought my daughters this little bunny that they push a button on the bunny and it's really quite amazing, the first time you see it.

00:11:30

That's not a bunny. That's like, some kind of little devil or something but it's got this little bunny right here. That's kind of how I think about the bunny. You push the button on the little mitten and its ears start clapping and it sings, If You're Happy and You Know It. So it's very loud and its ears are always clapping,

00:11:47

so that's exactly what happened as I hear this bunny begin singing and I, exactly, right here. Something bad has happened. My brain is like bunny happy if I know and it just blanked out. So what was I talking about? TCP, oh yes. Okay, so if the network connection

00:12:02

goes down, right, TCP is going to fail. You're not going to see a notification message. It's just going to see, "Okay, TCP has failed. I'm not getting any keepalives, so I'm just tearing down the session to that neighbor. So, with that being said, bunny

00:12:16

is turned off. So we've got the tables themselves. Biggest thing to get used to, first off just like any routing protocol we've got our neighbor table. Great first step in troubleshooting is my neighbor there. But one of the weird things about BGP is this.

00:12:30

You've got a BGP table and you've and a Routing table. I compared this a lot to the EIGRP topology table because it's kind of the same thing. BGP, let's say you've got a connection up here to ISP1, I'll just put I1 and I2, ISP1 and ISP2. They're going to send you all the routes, BGP and I should emphasize, they're best routes. The ones that they're

00:12:56

actually using that are in the routing table because they may have some uplinks to ISP three, four, five, six over here, they're going to send you everything. They're just going to get the best routes from each of those and then send you those. But that internet

00:13:06

of itself, if that's an internet connection has a lot of routes. So you're getting the full internet routing table from ISP1 and ISP2. That's big. That's a lot of routes that are coming in there. All of those go into the BGP table. From there your router is

00:13:23

going to go through that BGP metric. Remember those ten attributes, the way, the local preferences, down the list we go. This is going to pick the best of those routes and it has a lot of criteria like, you have to be able to reach the next hop and there's a lot of troubleshooting that comes into that but the best of those routes are going to be moved into the routing table by the BGP, well it's going to go through the BGP scanning process and move those into the routing table and then you are going to send the best of your routes. So you're going to pick the best ones and

00:13:50

then send those to your neighbors via BGP. Let's say this is ISP9 over here. If you're a transit system you're going to pass those routes on and that neighbor is going to get the best from you and the list goes on and on. So you do a show IP BGP, you're

00:14:05

going to see everything in this BGP table. It's a good place to start digging if routes aren't showing up in the routing table. Am I receiving them, are they showing up with little asterisk next to them, all of those kind of things. Now excuse me, you're

00:14:18

going to be listed in the BGP table and then of course, we've got the routing table which is just like every routing protocol, list all the best routes that exist in your system. All right then. So let's take that and wrap all that up by looking at the key troubleshooting commands for BGP. First off, I know

00:14:38

that you know that BGP is just for gadgets, it's a giant protocol so we could put a billion trouble shooting commands up there. I just want to give you the core that work most of the time. I would say, cover most issues. First off, show BGP summary. I would say that is by far my favorite command for BGP because it shows your neighbors which I know you're looking two commands below this and you're thinking, well that would show your neighbors.

00:15:04

No, well it does, it does, but you're going to get like four pages of output for every single neighbor. It's going to be like, here's everything that I know about this neighbor. They're social security number, what lollipop flavor they like, everything.

00:15:14

And it's very hard to weed through and get that information you want. This is like that good all show IP interface brief to where you're just like, "Give me the facts and give it to me quick." You're getting a table list of what every single neighbor, the big thing that you're looking for is what state is that neighbor in. So, I should pull up, I should pull out an output of this

00:15:35

but you'll see when we see the troubleshooting thing. It's usually you'll see the IP address of the neighbor, their up time, blah, blah, blah. You're looking at the very very end of this command and it shows you the state. It'll either say, I think the title

00:15:48

is like, it's the state and then slash and then puts like, prefix is received. If there is any words listed in here, that's a bad thing. If you see idle, if you see active, if you see any word that is listed there, that means the neighbor is not working right. You wanted to see a number here. You want to see like

00:16:06

500,000 maybe not that many but maybe like 200,000 which tells you how many prefixes or network advertisements you've received from that neighbor. So that's your first troubleshooting command. Do you see the neighbors listed there. It does the state show

00:16:21

a number right there? If those two are good, then move on, do a show IP BGP. That's where you can see the entire BGP table that exists, so all of the prefixes that you're receiving, think of that as, like I said, your topology table, your link state database if you will, for BGP. But unbelievably,

00:16:40

BGP is a distance-vector protocol and when you really know the difference between distance vector and link state, it's not so hard to believe. Distance vector again, its core attribute is that it only knows what neighbors are telling. Link state knows everything in the system and when you think about this scope and scale of the internet, good grief, I mean no way to run BGP if it were link state protocol because it have to know everything about everything. Whereas, distance-vector, this is far more

00:17:08

reasonably, you only know what the neighbor has told you to know. It's just, again, when you our first introducing people to distance-vector and link state they're like, oh okay. So distance-vector is like this simple but like RIP routing protocol, I mean, that's why it gets in their mind and then when you say, well BGP is actually distance-vector like, oh, no way. That's amazing. So, anyway,

00:17:27

we're fast. Show IP BGP neighbors, I talked to about that one already. If you really want to get nitty-gritty, you want to know everything about everything about that neighbor that's the command you use, so a lot of times, too overwhelming to be useful.

00:17:41

And then you've got your two debug commands of depth. I say that because if you're not careful, if this is like an internet phasing router and you're receiving this from an ISP, for instance, if you're doing a debug IP BGP or an updates and you then cleared the neighbors, brace yourself. I mean, that's one of those could

00:18:01

end the routers life kind of commands to where the router could lock up because you're getting hundreds of thousands of updates from a neighbor about different prefixes so, there's just going be a lot shown on the screen. So definitely, if you do use these

00:18:13

commands to watch the communication, put some filters on it. Make sure that you're protecting yourself from getting too many updates from BGP. So that is BGP in a nutshell. If you're ready, I'm ready. Let's move into the troubleshooting. I hope this has been informative

Route TSHOOT: BGP

Route TSHOOT: Router Performance Issues Concept Review

Route TSHOOT: Router Performance Issues

Security TSHOOT: Access List Concept Review

Security TSHOOT: Access List Chaos

IPv6 TSHOOT: IPv6 and IPv6 Routing Protocols

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Jeremy Cioara
Nugget trainer since 2003