Cisco CCNA ICND2 640-816

Routing Protocols: OSPF Configuration and Troubleshooting

by Jeremy Cioara

Start your 7-day free trial today.

This video is only available to subscribers.

A free trial includes:

  • Unlimited 24/7 access to our entire IT training video library.
  • Ability to train on the go with our mobile website and iOS/Android apps.
  • Note-taking, bookmarking, speed control, and closed captioning features.
Video Title Duration
1. Review: Rebuilding the Small Office Network, Part 1
00:33:54
2. Review: Rebuilding the Small Office Network, Part 2
00:28:45
3. Review: Rebuilding the Small Office Network, Part 3
00:23:36
4. Switch VLANs: Understanding VLANs
00:16:09
5. Switch VLANs: Understanding Trunks and VTP
00:39:07
6. Switch VLANs: Configuring VLANs and VTP, Part 1
00:35:58
7. Switch VLANs: Configuring VLANs and VTP, Part 2
00:39:36
8. Switch STP: Understanding the Spanning-Tree Protocol
00:28:18
9. Switch STP: Configuring Basic STP
00:21:16
10. Switch STP: Enhancements to STP
00:29:54
11. General Switching: Troubleshooting and Security Best Practices
00:29:23
12. Subnetting: Understanding VLSM
00:18:42
13. Routing Protocols: Distance Vector vs. Link State
00:26:25
14. Routing Protocols: OSPF Concepts
00:30:36
15. Routing Protocols: OSPF Configuration and Troubleshooting
00:39:53
16. Routing Protocols: EIGRP Concepts and Configuration
00:32:28
17. Access-Lists: The Rules of the ACL
00:27:44
18. Access-Lists: Configuring ACLs
00:34:40
19. Access-Lists: Configuring ACLs, Part 2
00:48:42
20. NAT: Understanding the Three Styles of NAT
00:20:00
21. NAT: Command-line NAT Configuration
00:35:41
22. WAN Connections: Concepts of VPN Technology
00:33:20
23. WAN Connections: Implementing PPP Authentication
00:34:39
24. WAN Connections: Understanding Frame Relay
00:28:42
25. WAN Connections: Configuring Frame Relay
00:30:52
26. IPv6: Understanding Basic Concepts and Addressing
00:33:59
27. IPv6: Configuring, Routing, and Interoperating
00:23:36
28. Certification: Some Last Words for Test Takers
00:13:10
29. Advanced TCP/IP: Working with Binary
00:25:51
30. Advanced TCP/IP: IP Subnetting, Part 1
00:55:06
31. Advanced TCP/IP: IP Subnetting, Part 2
00:22:29
32. Advanced TCP/IP: IP Subnetting, Part 3
00:19:53

Review: Rebuilding the Small Office Network, Part 1

Review: Rebuilding the Small Office Network, Part 2

Review: Rebuilding the Small Office Network, Part 3

Switch VLANs: Understanding VLANs

Switch VLANs: Understanding Trunks and VTP

Switch VLANs: Configuring VLANs and VTP, Part 1

Switch VLANs: Configuring VLANs and VTP, Part 2

Switch STP: Understanding the Spanning-Tree Protocol

Switch STP: Configuring Basic STP

Switch STP: Enhancements to STP

General Switching: Troubleshooting and Security Best Practices

Subnetting: Understanding VLSM

Routing Protocols: Distance Vector vs. Link State

Routing Protocols: OSPF Concepts

Routing Protocols: OSPF Configuration and Troubleshooting

00:00:00 - It is now time to take the concepts we've learned and apply
00:00:04 - them in OSPF configuration and troubleshooting. We're going
00:00:08 - to look at, as we walk through here, at the general syntax;
00:00:10 - that's how we'll start off, we'll look at the diagram, we'll look at the
00:00:13 - general syntax to set up OSPF and get it running on all our routers.
00:00:17 - As we do that, we'll be verifying what we're doing. You can see verification
00:00:21 - is my final thing but we'll be verifying what we're doing as
00:00:23 - we go. The 2nd concept I'm going to talk about is the router
00:00:27 - id or the name of the router. How what what importance that
00:00:30 - has and how to set that? Then finally we'll look at the verification
00:00:35 - and troubleshooting commands with OSPF. So let's get going.
00:00:39 - Configuring OSPF is not much more difficult than
00:00:43 - configuring most of the routing protocols but there are a couple
00:00:46 - of tweeks that I need to show you. First off, here's our network
00:00:49 - diagram that we've been using thus far and will continue to
00:00:51 - use. We've got router 1, router 2 router and router 3. Now, as of right
00:00:55 - now they're all running RIP and we're going to convert that
00:00:57 - over to run OSPF. Now if I were to diagram out my areas and this
00:01:02 - is going to be a really rough sketch, I would go in here and I would
00:01:06 - say this: Router 1 encompass all the way down here. Router 2 and what I'm going to
00:01:12 - do is this
00:01:15 - is all area 0.
00:01:20 - Now the first thing I want to mention is that the CCNA exam;
00:01:25 - if you are a exam prep, the CCNA exam only tests on
00:01:30 - something known as single area OSPF which in my opinion, ah
00:01:37 - okay; a lot of people run OSPF in a single area. A lot of small
00:01:42 - to medium size networks which is why they they test on it in
00:01:45 - the CCNA. The CCNA is meant to operate in those environments
00:01:49 - but to really understand the power that you have with OSPF you
00:01:52 - gotta see multi area configurations. So forgive me. I'm going
00:01:57 - to add it in here. We're going to make this area 1. Now it
00:02:03 - a multi area configuration is so much; well I will say it
00:02:07 - is is so little more this is horrible english here. There's
00:02:12 - not much more to it is what I'm trying to say. You're going to see
00:02:15 - the single area config. I'm just gonna add one or two more commands and
00:02:19 - you'll see it convert to a multi area configuration. You can
00:02:22 - see this, to simulate this environment because we only have three
00:02:24 - routers here, I'm going to pretend that that router 3 has connections;
00:02:29 - all these 172.16 networks in area 1. We 're going to
00:02:32 - break it off and we're going to summarize. It's going to be awesome, I'm telling you.
00:02:35 - So that's the script ; so, first thing I'm going to do, is I'm going to hop over to router 1.
00:02:40 - Let me get my terminal ready ready here.
00:02:46 - Bring it into view; here we go. I'm sitting on the access server.
00:02:51 - I'm going to router 1. I'm going to type in show ip protocol just to
00:02:54 - verify; Yep RIP is still running. Let's kill it. You go in and
00:02:58 - type in no router rip which turns off rip on router 1. Hangs there for a moment
00:03:03 - because it's shutting down the whole process and now we're going
00:03:06 - to add OSPF. We've got no routing protocols running, so I'm going to type in
00:03:10 - router OSPF followed by a process ID.
00:03:16 - Now this process ID just identifies the process on your
00:03:22 - router. For example, if you go on Windows and open task manager;
00:03:26 - let me see if I can open it here. Right here I've got all of these different processes
00:03:30 - running in in Windows will actually identify them all by a
00:03:33 - process ID and if you get into in depth you know how task manager
00:03:38 - operates you're able to kill processes with Windows, same thing
00:03:41 - with Linux. Well in a router you need to identify what process
00:03:44 - ID this OSPF will be identified as. It does not have to
00:03:48 - be the same on all the routers, I could use 1 on router 1
00:03:52 - and 50 on router 2 and 6000 on router 3 but
00:03:56 - with that in mind most people will make it the same on all your
00:03:59 - routers because if you make em different you have to remember
00:04:01 - it on every router you go to. So I like using router OSPF 1.
00:04:07 - Now once I'm under here, I need to type in my network commands.
00:04:10 - Now think back to RIP. The network command does two things.
00:04:15 - It identifies what networks to advertise for example when I identify
00:04:19 - and say 192.168.1.1. This network will
00:04:22 - be advertised this direction, it will say:" I know about 192.
00:04:27 - 168.1.0/24 and
00:04:31 - I will advertise that network and the second thing the network
00:04:34 - command does is say: "Send hello's in this direction".
00:04:39 - Now with RIP there is specific ways we had to type in the network
00:04:43 - statement and samely so with OSPF. OSPF has a very specific way
00:04:47 - to type it in which is far more flexible than RIP but also keep in
00:04:50 - mind I've got my internet connection running over here. Do
00:04:54 - I wanna advertise that to the rest of the OSPF domain;
00:05:00 - no, and in the same way do I want to send hello packets
00:05:03 - out here? no, because that's not secure. I don't want my ISP
00:05:07 - to form an OSPF neighbor relationship if they want
00:05:11 - to do so this interface will be exempt from both of those
00:05:15 - criterias. Now I know some of you might be thinking well you want
00:05:19 - the routers in your network to access the internet right? You
00:05:23 - got the internet right over here so shouldn't you advertise this link to
00:05:26 - em; well yes, we do want them to access the internet but
00:05:30 - at the same time advertising this link will not allow that.
00:05:34 - That will just allow them to access this link. We need to advertise
00:05:37 - in a default route meaning all 0's remember that 0 0
00:05:41 - 0 0 route. We need to advertise that in into the network
00:05:45 - so everybody has a default route out of the corporate
00:05:48 - network so, we'll have to remember to do that. First off let's
00:05:52 - turn it on on router 1
00:05:54 - and then jump back to my terminal and I'm gonna type in network
00:05:59 - followed by what network I want to advertise. In this case, flip back; I'm
00:06:04 - doing 192.168.1 so 192.168.1.0
00:06:07 - is what I'm going to advertise. Now this
00:06:12 - is the same so far as RIP right. In RIP
00:06:16 - we would type in the classfull network we want to advertise. 192.168.1
00:06:19 - is a class C network so I type that
00:06:22 - in but OSPF requires, notice, incomplete command. It requires
00:06:27 - that I add on something known as an OSPF wild card mask
00:06:32 - woww the wild card mask, I love this concept. It is unnecessarily
00:06:38 - complex for for for no good reason. Everybody that
00:06:43 - I've taught this to is like why did they do it that way. I don't know just
00:06:47 - because that's that's what CISCO does and this isn't just a
00:06:51 - CISCO thing. Just about every router will require wild card
00:06:55 - bit so what is a wild card ? What it is is kind of like a
00:07:00 - match statement. Here is the idea. I'm going to come back over
00:07:04 - here and if I were to go to router 1 and type in
00:07:08 - network,
00:07:10 - where is my pen 192.168.1.0. I have
00:07:15 - to follow that up with wild card mask and a wild card mask; the simplest
00:07:18 - way I can define it is exactly the opposite of a subnet
00:07:23 - mask so, I would go in here and do 0.0.0.
00:07:28 - 255 what? That's right. Remember our subnet mask is 255.
00:07:33 - 255.255.0 that's class C.
00:07:37 - A wild card mask is exactly the opposite. If you want the simple
00:07:41 - formula just take 255.255.255.255
00:07:45 - and subtract your subnet mask from this and you'll get 0.0.0.255.
00:07:49 - That's how you figure out a wild card mask. Now
00:07:52 - I know you're looking at that going I don't need a formula
00:07:55 - for that but when we get to access lists, you'll thank me for that.
00:07:59 - Here's what it means? I know just throwing this out there doesn't mean anything.
00:08:03 - Anytime you see a zero in your wild card mask, line it up and match
00:08:10 - to the network that you've typed in so; zero matches here
00:08:15 - zero matches here, zero matches here.
00:08:20 - In deeply technical terms that means look at these meaning
00:08:27 - look for interfaces that begin with 192.1
00:08:32 - 68.1.0. The 255 means
00:08:38 - in technical terms I don't care.
00:08:44 - What that does is now instruct the router when I type in that
00:08:47 - wild card mask; look for interfaces on yourself. You've got
00:08:52 - ethernet 0/0. Look for interfaces that start with 192
00:08:55 - is the first one. Look at these 168 is the second
00:08:59 - one, one as the 3rd octet and then I don't care what
00:09:02 - comes after that, in this case we have a.1 on the interface
00:09:06 - but it's saying I've got a.0 but this could be anything
00:09:09 - from 0 to 255. You could have any IP address on
00:09:11 - here that starts with 192.168.1 and OSPF
00:09:14 - will say:"I don't care about this last digit right here. I'm going to run
00:09:17 - OSPF on that interface." So
00:09:21 - this gives me a more flexible way of identifying interfaces.
00:09:25 - For example, let's let's jump down to router 2 here. If I
00:09:28 - was on router 2; check it out. I've got 192.168.1 and
00:09:33 - in one network. 192.168.2 in another network
00:09:36 - over here and 192.168.10 and 20 as
00:09:39 - sub interfaces that are routing between my VLANs here. Now if
00:09:43 - I were to do this with RIP or with a wild card mask of this,
00:09:48 - I would have to type in 4 network statements. Network 192.168.
00:09:52 - 1.0.0.0.0.255 is a wild card mask.
00:09:55 - Network 192.168.2.0.0.0.0.255 is a wild card mask.
00:09:59 - So you can see it's kind of an efficient so I
00:10:02 - could go in there and say:"Well I'm going to type in network
00:10:06 - 192.168.0.0.0.0
00:10:12 - any guesses?
00:10:16 - 255.255. Again what this means is I will
00:10:22 - run OSPF and advertise any network that starts with 192
00:10:26 - look at this 168 look here 255 says I don't
00:10:31 - care" and "I don't care" so immediately OSPF goes on the router
00:10:35 - and begins looking at all of the routers interfaces and
00:10:38 - goes oh; well this one starts 192.168 and I don't
00:10:41 - care what comes after that. This one over here starts with
00:10:44 - 192.168 and I don't care what comes ; wow my
00:10:47 - pen got bigger. I think I clicked something or something. This starts with
00:10:50 - 192.168 you know, over here I don't care; so it's looking
00:10:54 - and identifying every interface that starts with that 192.168.
00:10:57 - That's the power of the wild card mask
00:11:02 - is it gives us the flexibility of what to type in. I'm going to give you one more
00:11:05 - example. Let's say I'm on router 3
00:11:10 - and I only; let me see if you can pick up my point here. I only want to
00:11:16 - run OSPF on specifically
00:11:21 - this interface. I don't want any other interface in here to run
00:11:25 - OSPF, no matter if I add interfaces in the future I want to
00:11:28 - make sure that only that interface will run OSPF.
00:11:35 - Are you catching my hint? I'm gonna type in to do that network
00:11:40 - 192 with my big kindergarten
00:11:44 - marker here, 168.2.2 with a wild card mask of
00:11:49 - 0.0.0.0.
00:11:53 - Ahaa that says: run OSPF on specifically, look at this, look at
00:11:58 - this, look at this look at that. Every part of that IP address
00:12:03 - is specifically identified so it will only run on there. Now I
00:12:07 - use this wild card mask all the time not only because it gives
00:12:11 - me complete control of how OSPF operates, meaning I get to identify
00:12:17 - exactly the interface it's going to run on but also it eliminates
00:12:22 - a lot of complexity in my own mind of what I need to type
00:12:26 - in. I mean if you think about, if you want to run OSPF on
00:12:30 - a router all you gotta do is go to that router and type in, let
00:12:33 - me do a do command do and if you haven't seen it do does
00:12:37 - show commands from any mode. Do show IP interface brief and
00:12:41 - I say ok those are my 2 interfaces so I'm just gonna identify
00:12:44 - that, you know, network 192.168.1.1.0.0.0.0
00:12:49 - is my wild card mask. That's what I would type in to start on
00:12:52 - just that. If I wanted to run it on my internet link i would type in 68
00:12:55 - 110.171.98 0000 and that would run it
00:12:58 - on exactly that interface. So that's that's how the OSPF
00:13:02 - network command works. Let me clean up all this gibberish
00:13:06 - there we go, that looks a little better. Now let's get into the configuration.
00:13:10 - So I'm gonna go to router 1
00:13:13 - and type in network. Well let me just do that show IP interface
00:13:18 - brief, do and I'll do network 192.168.1.1
00:13:26 - and I'll use my short cut 0.0.0.0 and let's
00:13:30 - see what it's looking for next.
00:13:32 - Area up and then what area do you want and I can type it in and
00:13:37 - we've we've already determined area zero is the backbone. It's
00:13:40 - always the first area that you configure good, so by typing
00:13:45 - that in I am now running OSPF on that interface and I'm
00:13:50 - advertising the network that belongs to that interface 192.168.1.0/24
00:13:53 - out into the rest of the
00:13:58 - world. Now I want to make sure I emphasise because this this
00:14:00 - boggled by mind when I got into CISCO. What you type in here
00:14:04 - is not what you advertise. You are not advertising 192.
00:14:07 - 168.1.1. You are advertising
00:14:11 - the network that belongs to that interface. When I type in show IP
00:14:14 - interface and look the 192.168.1.0
00:14:18 - /24 network belongs to that interface.
00:14:22 - So that's what you're advertising. So I can type in show IP
00:14:25 - protocol now
00:14:27 - and see I am running OSPF. I'm currently routing for that
00:14:31 - network which belongs to area 0. My router ID is this that's
00:14:35 - the name of the router and we'll talk more about that in just a moment
00:14:38 - and so what first router is done. Now I'm not going to have
00:14:41 - any routes because I haven't formed any neighbors. We'll see a
00:14:44 - command show ip ospf
00:14:46 - neighbor, which will show your neighbors, none, I have no friends
00:14:51 - so sad. So router 2 over here says " I need to join this
00:14:55 - OSPF network", so let's hop down there.
00:14:58 - Router 2 and I'll do configt no router rip, good bye rip. It is
00:15:04 - now disabled on router 2. Router OSPF 1. Let me do that do show
00:15:10 - IP interface brief and there's all my interfaces on there.
00:15:13 - Let's use the the wild card mask to our advantage here. I'm gonna do
00:15:17 - network 192.168.0.0
00:15:23 - 0.0.255.255 and remember
00:15:28 - that says I care about any interface starting with 192.168
00:15:31 - that's all of my interfaces on this router. I will add
00:15:34 - those to area 0. The other area the other part of the ip
00:15:39 - addresses I don't care about, so all the interfaces on here
00:15:42 - will begin running OSPF as soon as I type this in.
00:15:46 - I hit enter. We're now running OSPF on all those. Let me do a
00:15:49 - show ip ospf to prove it. I can see that, oop that's not what I want; show ip
00:15:55 - protocol. Oh check that out. I was trying to get there before our
00:15:57 - neighbor would form but,
00:16:00 - good grief I'm just not lucky here.
00:16:04 - Show ip protocol. We see I'm running OSPF. I'm routing for all
00:16:08 - the networks that start with 192.168 my router
00:16:12 - ID or the name of my routers 192.168.20.1
00:16:15 - so when I do a show ip ospf neighbor;
00:16:20 - now look at that. I have formed a neighbor on OSPF.
00:16:25 - They are 192.168.1.1.
00:16:28 - Their IP address is 192.168.1.1
00:16:31 - this is the router ID the name of them this is
00:16:33 - the IP address I use to communicate and this is the interface
00:16:36 - I go out to speak to them. Look back at our diagram and we
00:16:40 - can see sure enough that's router 1. This is us router
00:16:43 - 2 and we're speaking out fast ethernet 0/0. Now let's hop back up
00:16:47 - to router 1
00:16:52 - and do a show ip ospf neighbor here as well. I can see that
00:16:57 - I have a neighbor 192.168.20.1 that's
00:17:00 - their router ID the name of the router, but I'm communicating
00:17:03 - with them on the IP address 192.168.1.2. Again,
00:17:07 - I have a whole slide dedicated to the router ID in just
00:17:10 - a moment but for now I can see I've formed neighbor relationships
00:17:13 - so when I do a show ip route I expect to see drum roll please,
00:17:19 - OSPF routes. Check it out there they are: OSPF 192.168.2.0,
00:17:24 - OSPF 192.168.10.0
00:17:28 - ohh look at that. I have a static route I had that in there
00:17:32 - from when we were doing our VLAN labs. Let me do a show
00:17:35 - run, check this out. I'll show you a cool short cut include lines that have ip
00:17:40 - route in them because my static routes are IP route so I
00:17:43 - can go in there. I want to remove my static route I don't need it
00:17:46 - any more. OSPF is doing it for me no pasted in there IP route. That's exactly
00:17:52 - what I had in my running config so I'm removing that. Now when i jump back
00:17:55 - I expect to see my static route replaced by an OSPF
00:18:00 - route, good. We don't need statics any more. OSPF is doing the work
00:18:03 - for us. So we're now learning all of these routes via OSPF
00:18:08 - and I have my default route down here going to the internet.
00:18:12 - Let's just see something. Let's jump down to router 2 and
00:18:15 - see if it knows about the default route. Do a show ip
00:18:20 - route. Ah bummer. Look at that, no default route which means no router 2 getting
00:18:25 - to the internet.
00:18:27 - Let me show you how OSPF takes care of that? On router 1 the one
00:18:33 - with the default route
00:18:36 - I can go under the OSPF process and type
00:18:42 - a single command "default-information
00:18:47 - originate" think about that command. Any default information
00:18:52 - that you have a.k.q default route, go ahead and originate that
00:18:57 - meaning send that into OSPF so, send that to other routers. Now
00:19:02 - when I go back down to router 2 show ip route;
00:19:07 - sweet, look at that OSPF route is now shown up on router 2.
00:19:12 - Router 2 now has an, this is E2 external type to route to
00:19:17 - the internet through router 1. Now as this is where I
00:19:21 - lead you into the CCNP. In the CCNP you'll learn the difference
00:19:25 - between external type 1 and external type 2 routes and what
00:19:28 - those are all about but for now router 2 has a default route
00:19:31 - and should be able to get to the internet once we set up NAT
00:19:34 - and that's coming. So router 2 is now good to go. Now let's
00:19:38 - hop on over to router 3 because router 3 is still running RIP.
00:19:46 - I'll go to 3 no router rip good bye. I'll do router ospf 1 and underneath
00:19:53 - router 3 let me do a show IP interface brief. I can
00:19:59 - see that I have my ethernet interface right here, that's
00:20:02 - connected to the lan. My serial which links back to the wan
00:20:06 - and then all these quote unquote simulated networks they're
00:20:11 - considered loop back networks with all these IP address and
00:20:14 - that matches the network diagram over here. I'm going to show you
00:20:16 - first off area 0 getting NAT set up and then I'll add
00:20:20 - in our multi area so I'm gonna type in network, let's do the same thing
00:20:24 - here 192.168.0.0.0.0.255
00:20:29 - 255 area 0.
00:20:32 - That will add any interface with 192.168
00:20:35 - in front of it to area 0 and you can see I formed a neighbor
00:20:39 - relationship. I can do a show ip ospf neighbor
00:20:45 - and there I see my neighbor. I can type in show ip route and
00:20:50 - my router is now receiving OSPF routes, even the default
00:20:54 - route from over at routef 1 so it is able to get out and access
00:20:58 - the internet. So with that in place and I can tell you that's
00:21:04 - virtually what you need to know for the CCNA exam.
00:21:07 - That's how you set up OSPF in a single area. Let me expound now.
00:21:12 - Let me have the chains released and I will add in area 1.
00:21:17 - I'm going to go in and I'm gonna type in network 192 dot, oh
00:21:22 - wait a sec; 172.30 cause I've got 172., oh no
00:21:26 - I don't match what I really have these are 172.30
00:21:30 - networks. I accidentally put 172.16 over here
00:21:34 - on the diagram so imagine pretend those all say 192.168
00:21:38 - .30 and then I have a 0 1 2 3 4 5 6
00:21:42 - 7 you wanna see something fancy. I'm going to show this to you because we're
00:21:47 - going to need it when we get to access lists but how would
00:21:50 - I create a summary route for those. Well think back to the previous
00:21:54 - video when we talked about route summarization. I would go in there
00:21:58 - let me actually type this, this will be a little cleaner than
00:22:03 - trying to scribble it in there. Get myself a bigger font. 172.16
00:22:07 - and this is 172.30, sorry I mistyped those,
00:22:11 - 0.0 in binary 172.30
00:22:16 - is the same between all of them. The 3rd octet is what I'm concerned
00:22:19 - with so, let me go in there in binary is all 0's eight 0's
00:22:24 - and the last one is all
00:22:27 - zeros but let's just focus on the 3rd. I'll just do first three octets.
00:22:31 - One is172.30.00000001; Two, 172.30.0000
00:22:37 - 10 that's 2 in binary; three 172.30.
00:22:44 - 11 you're getting the idea? So if I already go all the way down to 7
00:22:47 - dot dot dot, 7 would be 172.30. 1
00:22:51 - 2 3 4 this will be 16 8 4 2 1 that
00:22:57 - is 7 as a binary number. So by grouping all those together
00:23:01 - I am able to say that 172.30.0 through
00:23:05 - 7 have the first let's see we've get
00:23:08 - 8 bits in common 8 bits in common so that 16 17 18 19 20
00:23:16 - 21. So this is my dividing line. You can see this is where
00:23:20 - 0 through 7 are all different so I can say that I have
00:23:23 - 5 bits here so a summary route for 172.30
00:23:28 - .0.0 through 172.30 is 7.0
00:23:32 - is 172.30.0.0/
00:23:37 - 16+5 is 21 or if I were writing that summary route
00:23:41 - in decimal 172.30.0.0
00:23:46 - with the subnet mask 255.255./21
00:23:51 - would be 248.0.
00:23:54 - That would be the decimal version of the subnet
00:23:57 - mask so, that's a summary route that groups all of those up.
00:24:01 - Now let me show, now this is; what I'm going to show you is just
00:24:04 - at this point showing off not not showing myself off but if
00:24:09 - you were to do this for somebody you'd be showing off but I'm
00:24:11 - going to demonstrate a skill that is going to give you great
00:24:15 - success when you to access lists. What wild card mask could
00:24:20 - I type on router 3 that would run OSPF on just those
00:24:25 - interface? We have a subnet mask that says:" this subnet mask
00:24:29 - matches you know 172.30.0 through 7
00:24:34 - or summed up in this. Remember the formula I gave you
00:24:37 - how do you figure out a wild card mask? You take all 255's
00:24:43 - and subtract the subnet mask. I'm going to subtract that summary subnet mask
00:24:48 - 248.0=0.0.7
00:24:55 - 255-248 is 7.255
00:24:59 - 255-0 that is a wild card mask.
00:25:04 - That will run that I can I use to identify to run OSPF on
00:25:08 - only interfaces starting with 172.30.0
00:25:13 - through 7 because this is a summary route that encompasses
00:25:17 - networks 172.30.0 through 7.
00:25:21 - Now like I said, this is just showing off because you can accomplish
00:25:25 - the same thing by going in here and typing 172.30.0.0
00:25:28 - with a wild card mask that looks like that and
00:25:33 - that would work because all these interfaces start with
00:25:36 - 172.30 and you know that's what we're
00:25:40 - saying is important here but we can also do 172.30.0.0.0.0.7
00:25:44 - .255
00:25:49 - and that would say run OSPF on any interface that starts with
00:25:54 - 172.30 and because of this it's saying it and has
00:25:58 - 0 through 7 in the 3rd octet.
00:26:03 - That's how to impress your friends but when we get to access
00:26:06 - lists that will become an invaluable skill because that will
00:26:09 - help us be very specific with what we want to deny or allow.
00:26:13 - More on that later. For, for now I'll use our bragging wild card
00:26:18 - mask there and I'll say: "this is in area 1"
00:26:24 - because looking at our diagram that's where where we are. So when
00:26:28 - I hit enter I have by typing that one command created an ABR,
00:26:34 - an area border router that is routing between
00:26:40 - two separate areas. Now that that that is all there is to
00:26:44 - it. There's no I'm an ABR command so, I can go in there and
00:26:47 - type show ip
00:26:49 - protocols and I can see that I'm routing for 192.168.00 in area
00:26:54 - 0 and I'm routing for this network in area 1.
00:27:00 - Now when I go back to router 2 check it out; I'm going to go to router 2
00:27:04 - and do a show ip route.
00:27:07 - Ohh that's awesome, awesome look at that. We have OSPF
00:27:11 - routes in our table, the default route that router is getting
00:27:15 - from router 1 and remember where router 2 is. Router 2 is right here.
00:27:18 - It's only going to learn about the default route because it already
00:27:21 - knows about all this network over here and it's going to
00:27:24 - learn about this route the 3.1 in its own area and
00:27:27 - all these are in area 1 and look at this; there is the 3.
00:27:31 - which is is just a normal OSPF route and all these are area
00:27:37 - 1 routes a.k.a. Inter Area, see that little ia there. That is
00:27:42 - identified as an inter area route. Now as I mentioned if you're
00:27:46 - just breaking into multiple areas and not doing summarization
00:27:50 - you're doing no good and this is something I mentioned in the
00:27:52 - previous video because that's the whole point of breaking into multiple
00:27:56 - areas is now you can summarize. Now I know I know I'm going
00:28:00 - beyond the CCNA here again, let me emphasize CCNA
00:28:03 - is just a single area but I've got to show you this one final
00:28:07 - command. I'm gonna go ohhh, holy cow;
00:28:10 - there's Vista for you. I'm going to go to a the router 3 and
00:28:17 - I'm going to type in
00:28:21 - router ospf 1 and I'm going to do area 1 range and then
00:28:30 - what I want my summary route to be. Now we already figured it
00:28:34 - out right here in our binary our summary route for area 1
00:28:38 - to encompass all 7 of those networks will be 172.30.0.0/21
00:28:41 - or with this
00:28:46 - subnet mask behind it that's a good summary route to encompass,
00:28:49 - just those 7 networks. So I'm gonna jump back over here, and do area 1 range
00:28:54 - 172.30.0.0 followed by a
00:29:00 - normal subnet mask no wild card mask 255.255
00:29:04 - .248.0 done. I have now encompassed and I've told
00:29:11 - router 3 which is an ABR
00:29:13 - the range for area 1 is 172.30.0.0
00:29:18 - with this subnet mask which emphasizes 0 through 7. Now let's
00:29:23 - let's check this out. I'm gonna go back to router 2 and do a show ip
00:29:27 - let's check this out. I'm gonna go back to router 2 and do a show ip route.
00:29:29 - Look at that. Isn't that ohh, I'm telling you, you'll get this excited
00:29:34 - when you get into OSPF. We've got this which it is shows /21.
00:29:38 - It even did the the mask for us. It said you typed in that subnet mask
00:29:42 - which is also a /21 there and you can see right
00:29:45 - there is subnet and we have 1 inter area route that is available
00:29:49 - to us, a summary route. Notice all 7 of those previous routes
00:29:53 - that we previously were looking at in that routing table have
00:29:56 - disappeared and been replaced by one summary route. Now watch this, watch
00:30:00 - this. Hang on, ah am I going too far. I'm going too far but I've
00:30:04 - got to do this one more thing. I'm going to create one more network.
00:30:09 - You see my loop back interfaces right here 172.30.
00:30:13 - 0 through 7. I'm going to create one more. I'm going to do interface loop back 8.
00:30:17 - This is how you can simulate networks by the way and I'm gonna do ip address
00:30:22 - 172.30.8.1. I'm gonna add another
00:30:27 - network that's not part of the summary mask because if I go
00:30:31 - down here; 8 in binary I'm running out of room man, I'm gonna say
00:30:35 - 8 is 0 0 0 0 1 0 0 0 that's that's 8 in binary
00:30:40 - which does not have the first 5 bits in common which goes outside of
00:30:43 - our summary mask and when I add that in their, ohh wait a second.
00:30:49 - I used the custom wild card mask to add that to OSPF didn't I. We'll have
00:30:53 - to do something; ignore what I'm typing right here. Just ignore it you're
00:30:58 - not you're not seeing what i'm typing.
00:31:02 - Did you see that I didn't see that and I'm going to type in network
00:31:06 - 172.30.8.0
00:31:11 - with that as my wild card mask. So I've added that network to OSPF because with
00:31:15 - our custom wild card mask before we just added 0 through 7
00:31:18 - that manually added 8 in there. Now, if I go back to router
00:31:21 - 2 show ip route.
00:31:26 - Look at that it's separate. The summary doesn't encompass it
00:31:30 - because the summary only includes 1 through 7 so, what
00:31:33 - what we've proved by doing this is that our custom summary mask
00:31:37 - is working perfectly encompassing just the networks that we
00:31:40 - wanted to. So yes we did go beyond the CCNA but that
00:31:44 - is multi area OSPF that is a big part of the CCNP.
00:31:50 - Woo, I've got to breath here. OSPF is exciting. I'm telling you it is a very
00:31:53 - cool protocol. Our last few concepts we'll talk about in this
00:31:58 - video is number 1: understanding the router ID and then number
00:32:01 - 2: we'll just look at how to trouble shoot OSPF which is
00:32:04 - really focused around one thing. So the OSPF router ID
00:32:08 - is the name of the router. We've seen it a couple times when
00:32:12 - we were going in. If I'm on, let's shoot over to
00:32:16 - router 3 and do a show ip ospf neighbor. Router 3
00:32:21 - sees router 2 as the router id or neighbor id 192.168.20.1
00:32:25 - but it communicates to router
00:32:30 - 2, its neighbor on the address 192.168.2.1.
00:32:35 - If we look back at our network diagram, where did that go, diagram, that's
00:32:40 - that's right you can see right router 3 communicates to
00:32:42 - router 2 on 192.168.2.1.
00:32:47 - So why is router 2 identified as that 192.168.20.1
00:32:54 - when we're looking at router ID. You can see
00:32:57 - .20.1 that's it's router ID. That's because of this
00:33:01 - rule. The OSPF router ID identifies the router to neighbors.
00:33:05 - It's the name of the router.
00:33:07 - It is by default the highest physical interface at startup.
00:33:11 - So if you've got this router sitting right here and you start
00:33:15 - the OSPF process and router OSPF 1 and you go in there, the
00:33:19 - router id will be this guy;
00:33:23 - the highest physical interface 210.62.58.1
00:33:27 - beats this and beats that because it is the higher
00:33:30 - interface. Now loop back interfaces also beat physical so
00:33:35 - if I go in there and add a loop back interface of 1.1.1.1
00:33:38 - an extremely low IP address; since it's a loop
00:33:42 - back it automatically wins. Now if I add another loop back of
00:33:46 - we'll say 5.1.2.1 this one now wins because
00:33:50 - it's the highest loop back
00:33:52 - and there is a new command router-id the new router
00:33:57 - ID command beats all. So let me show you what what this looks
00:34:00 - like. I'm going into router 2; we're on router 3
00:34:05 - why not stay there. I'm going to go and do router
00:34:09 - ospf 1 and I can hard code in there and a lot of people will
00:34:13 - do this router-id 3.3.3.3
00:34:17 - enter. Now that is the new name of the router and it says in order for this to
00:34:22 - take effect you have to reboot the OSPF process, so I'll add in here clear
00:34:26 - OSPF processes. It says are you sure; yes not something you want to do
00:34:30 - during production time but this will take down the neighbor.
00:34:33 - You can see that the neighbor is gone from full to down and
00:34:36 - then reload it and it went back in and it's now full again, neighbor reformed.
00:34:40 - So I go over to router 2 and do a show ip ospf neighbor and
00:34:44 - now I can see, see that 3.3.3.3, that's the name of
00:34:48 - router 3 that it sees and communicates with router 3 using
00:34:51 - the IP address 192.168.2.2. Now, at this level
00:34:55 - we're only mentioning the router ID as I just say that's
00:34:59 - the name of the router but as you get into the CCNP world
00:35:03 - you'll see that the router ID has a lot more ramifications.
00:35:06 - There are commands that you type in that require you to know
00:35:10 - the name of the remote router the router ID so, at this point that's
00:35:14 - just what the router ID is.
00:35:17 - Finally as we move into trouble shooting OSPF this slide
00:35:22 - should look somewhat familiar to you. This is the same slide
00:35:25 - we looked at in the previous video when we talked about how
00:35:28 - routers form neighbor relationships. 90% of your troubleshooting
00:35:33 - on OSPF is focused around routes not showing up because
00:35:36 - neighbors aren't forming so the best thing that you can do as
00:35:40 - you troubleshoot is to do that show ip ospf neighbors command.
00:35:44 - Do you see a neighbor there? Chances are if you are not seeing routes
00:35:47 - you're not seeing a neighbor so you're going to go through and
00:35:50 - mainly look at these criteria. Do the hello and dead timers match
00:35:55 - between me and my neighbor. Are we using the same subnet
00:35:58 - mask on the interfaces that we use to communicate? For instance,
00:36:01 - is this one a /24 and maybe this one a /25.
00:36:04 - Neighbors won't form. Are we in the same area? Has this one been
00:36:10 - defined in area 1 and this one definined in area 0. That would
00:36:14 - be a conflict. Neighbors. Wait a second
00:36:20 - that's not right. Neighbors this this shouldn't have a star
00:36:23 - forgive me if you jotted that down on a peice of paper it is it is
00:36:27 - not, that should not have a star. I can't believe I did that. Neighbors
00:36:32 - is a list of what neighbors each one of these knows about. It
00:36:35 - will say:" I know about these as my neighbors and I
00:36:38 - know about these as my neighbors", that's how the routers know and
00:36:41 - they send hello's back and forth if they're already neighbors
00:36:44 - or not if they see each other listed as a neighbor that does
00:36:47 - not have to match forgive me.
00:36:49 - Priority DR/BDR. Those are CCNP concepts but the
00:36:53 - password. If you are password protecting your OSPF network so
00:36:57 - routers can't just come in and join the routing fun without providing
00:37:01 - a password, it will say does the password match between these
00:37:04 - two routers? If not the neighbor relationships will not
00:37:07 - form so again, just going through and checking these 4 criteria
00:37:11 - hello and dead timers, the network mask, area id and password that will
00:37:16 - tell you whether or not these neighbor relationships are forming.
00:37:19 - If you want to trouble shoot this process even further the
00:37:24 - best way to do; let me get my
00:37:27 - thing moved in here is to do a debug ip ospf and its adjaceny;
00:37:32 - adj. That will show you the neighbor relationships forming.
00:37:36 - When I clear my process clear ip ospf process
00:37:41 - you actually see on the screen it shows neighbors going down
00:37:44 - and shows neighbors coming back up. It's a lot of info but this
00:37:48 - is a complete neighbor forming process between that was the
00:37:52 - second neighbor coming up and in everything it goes through as it
00:37:55 - forms a neighbor relationship. If there is a problem if there's an
00:37:59 - area in this match or a subnet mask it will be in this output that
00:38:04 - just scrolled up on my screen. It will say:"oh neighbors are not going
00:38:07 - to be forming because you know the area ID does not match
00:38:13 - area match conflict or because my authentication password fails
00:38:17 - so doing this one debug, will show the full neighbor process
00:38:21 - for me.
00:38:23 - Just walking through that simple configuration of OSPF I
00:38:26 - feel like there's this this can of OSPF concepts that I just want to
00:38:30 - open and just say let's talk about everything but, then this
00:38:35 - video would be 5 hours long and we would have a lot of
00:38:38 - stuff that does not relate directly to the CCNA. As you can
00:38:41 - hopefully get an idea of just by seeing this there is so
00:38:45 - much more that you can do with OSPF but that should give
00:38:48 - you enough at the CCNA level to set it up, to do basic
00:38:52 - route summarization that's even beyond the CCNA and understand; here's
00:38:56 - the key, you should be able to understand any OSPF config
00:39:00 - that you come across in the real world just by doing a
00:39:03 - show run and seeing what commands that have been typed in.
00:39:06 - To wrap up I want to hit the high points. We looked at the general
00:39:10 - syntax to configure OSPF. The major difference is that wild
00:39:14 - card mask with the network command. We then saw modifying the
00:39:17 - router ID, which is the highest physical interface by default,
00:39:21 - the highest loop back interface if you have one of those on your
00:39:24 - router and it can also be modified by typing router-id
00:39:28 - from router config mode and whatever you want your router ID
00:39:31 - to be.
00:39:32 - Finally, we looked at the verification and troubleshooting. Verification
00:39:36 - we did throughout the configuration looking at the routing
00:39:40 - table, looking at the neighbors and trouble shooting we did
00:39:42 - by looking at the debug command, debug OSPF adjacency, verifying
00:39:46 - that the hello parameters do match between two neighbors.
00:39:49 - I hope this has been informative for you and I'd like to thank you
00:39:52 - for viewing.

Routing Protocols: EIGRP Concepts and Configuration

Access-Lists: The Rules of the ACL

Access-Lists: Configuring ACLs

Access-Lists: Configuring ACLs, Part 2

NAT: Understanding the Three Styles of NAT

NAT: Command-line NAT Configuration

WAN Connections: Concepts of VPN Technology

WAN Connections: Implementing PPP Authentication

WAN Connections: Understanding Frame Relay

WAN Connections: Configuring Frame Relay

IPv6: Understanding Basic Concepts and Addressing

IPv6: Configuring, Routing, and Interoperating

Certification: Some Last Words for Test Takers

Advanced TCP/IP: Working with Binary

Advanced TCP/IP: IP Subnetting, Part 1

Advanced TCP/IP: IP Subnetting, Part 2

Advanced TCP/IP: IP Subnetting, Part 3

This forum is for community use – trainers will not participate in conversations. Share your thoughts on training content and engage with other members of the CBT Nuggets community. For customer service questions, please contact our support team. The views expressed in comments reflect those of the author and not of CBT Nuggets. We reserve the right to remove comments that do not adhere to our community standards.

comments powered by Disqus

Course Features

Speed Control

Play videos at a faster or slower pace.

Bookmarks

Pick up where you left off watching a video.

Notes

Jot down information to refer back to at a later time.

Closed Captions

Follow what the trainers are saying with ease.
Jeremy Cioara

Jeremy Cioara

CBT Nuggets Trainer

Certifications:
Cisco CCNA, CCDA, CCNA Security, CCNA Voice, CCNP, CCSP, CCVP, CCDP, CCIE R&S; Amazon Web Services CSA; Microsoft MCP, MCSE, Novell CNA, CNE; CompTIA A+, Network+, iNet+

Area Of Expertise:
Cisco network administration and development. Author or coauthor of numerous books, including: CCNA Voice 640-461 Official Cert Guide; CCNA Voice Official Exam Certification Guide (640-460 IIUC); CCENT Exam Prep (Exam 640-822); CCNA Exam Cram (Exam 640-802) 3rd Edition; and CCNA Voice 640-461 Official Cert Guide.


Stay Connected

Get the latest updates on the subjects you choose.


  © 2014 CBT Nuggets. All rights reserved. Licensing Agreement | Billing Agreement | Privacy Policy | RSS