Cisco CCNA ICND2 640-816

Routing Protocols: OSPF Configuration and Troubleshooting

by Jeremy Cioara

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Video Title Duration

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 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
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 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
00:07:45 - and subtract your subnet mask from this and you'll get
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 - is a wild card mask.
00:09:55 - Network 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 -
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 -
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
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
00:13:26 - and I'll use my short cut 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
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
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
00:15:23 - 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
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
00:16:28 - Their IP address is
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 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 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,
00:17:24 - OSPF
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
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
00:23:37 - 16+5 is 21 or if I were writing that summary route
00:23:41 - in decimal
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
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
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
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 - 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
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 - 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 -
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
00:32:25 - but it communicates to router
00:32:30 - 2, its neighbor on the address
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
00:32:47 - So why is router 2 identified as that
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
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
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 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
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, 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 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

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Jeremy Cioara

Jeremy Cioara

CBT Nuggets Trainer

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.

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