OSPF Network Types | Cisco CCNA 200-301

[Music] [Music] and welcome everybody whoo-hoo OSPF Network types is a topic we're gonna focus on today and I am so glad that you're here to join me in this discussion about a little a lot about OSPF and then also what the heck are OSPF network types and why do we care those are the two main homeruns we're going to focus on today so to do that I wanted to give a shout out to every who's joining us especially Pat and Mike and Gus and others I really I appreciate you being here as we take advantage of the time we have together to focus on you know cool topics and maybe reinforce things you already learn or learn something new for the first time so um let's do this in our goal of understanding OSPF let's take a look at the whiteboard and let me get out of a pen tool here and let's just talk just for a moment about OSPF char routers that we want to be OSPF neighbors in fact we should probably we should write to talk about what that means to be an OSPF neighbor won't you please won't you please won't you please won't you be my neighbor if we want routers to share information with each other like hey what do you know and what do you know let's show that information with each other so we can dine out the build routing tables building a neighbor ship or a full adjacency is when two routers they agree on everything they agree on what the subnet is between those two devices they do you know the mask of the exact same length same network they agree on things like what type of area is this what is the network we said that already what else they have to agree on all the timers like these little router we're going to send hello messages back and forth and the timers have to be exactly correct matching each other otherwise they won't become neighbors so the dead timers they have to be the same on both sides so another option is do we want to have a designated router yes or no on this network segment and all of those have to agree and if they do their routers are will build an adjacency and they'll be come with it called the little full adjacency they're sitting there sharing information back to forth they care about each other and it's a wonderful thing so what if there were a few parameters that we had to negotiate and we want to make sure we got them right every single time that is one of the aspects that a network type you know SPF can help us with and let's take a look at our topology and then I'll do a demo I'll show it to you in action so let's imagine that in fact let's start let's start with these two routers right here I've got router 1 and they need to get my pin out there we go why is my pin showing up Oh cuz it was white that's so funny it was white on white my bed alright so let's imagine we have router 1 and router 2 that are going to become OSPF neighbors meaning they're going to be able to share information with each other to to get that working we need to do a few things we need to go into router configuration mode on each of the routers router OSPF space and then we use a process number so if you are only running one process you can use process one or process ten it doesn't really matter press enter that puts you in router configuration mode and then we're gonna add Network statements in fact before we add Network statements I'm also gonna hard code a router ID and that's you don't have to hard code a router ID it'll go ahead and choose the IP address that's the highest IP address on a loopback if you have any loop backs or if you don't have those the highest IP address on a physical interface that's up but by hard coding the router ID for learning and also for documentation seeing where things are it makes a lot of sense so I'm gonna hard code the router idea in each of these devices and then I'm gonna use a network statement now here's here's how that Network statement operates and a network statement in OSPF says to the router dear mr. router I want you to play a matching game the router says what do you mean a matching Amy well here's I want you to do I'm gonna say network 10 anything and what I want you to do mister router is I want you to look at all of your interfaces that are up and if the network statement says 10 anything I want you to take a look at all the interfaces that start with the ipv4 address of 10 it doesn't matter what the rest is and include them as part of OSPF meaning you'll send updates and make do hello statements back and forth on those interfaces so the router says okay I get it and and that's what the network statement does it tells the router indirectly which interfaces based on their IP addresses should be included in OSPF so if we use the network statement like this network 10.0.0.0 if we wanted to tell the router you know what just match on this first 10 we don't care about the last 3 octet we would use what's called a wildcard mask and a wildcard mask we use in many places including OSPF Network statements and also in access control lists we use them as well so a wildcard good mask you like this 0 dot now that 0 here in the wild-card mask means we care about the first octet and then we add the last 3 octet as wildcards so effectively any where it says 255 it means the corresponding octet right here I don't care what it is right here I don't care what it is here I don't care what it is we can call the the bits that are on I don't care bits and so that is how you tell a router that any interfaces that have that begin with the 10 number 10 the first octet those should all become part of OSPF and then the other thing we need to add to is because OSPF can have multiple areas you know sometimes we need to carve things up to get stuff done like we have a huge like cleaning our house and all my that comes up from here right now anyway if you have to clean our house to do it all at once it's gonna take a lot of effort so what we could do is we could take chunks of it like okay I'm gonna do this part of the house now and this part later or if we had guests over and we were memorizing other people's names have everybody memorized every else's names that's a lot of work so we could per say okay your group a you memorize each other's names and Group B you memorize each other's names and Group C you memorize each other's names and in OSPF we can quarantine our group our routers in networks into groups and they call those areas just that a single router doesn't have to learn everything can you learn the routes in its area that it's in or cut there a couple two areas in areas that are 10 so the other thing I'm going to do here is we are also going to add we just Network statement when I specify what area those interfaces and those like you she'd go into sonar topology here I'm gonna specify that on these on router one and the interfaces that start with ten they should be put into OSPF and they should be put in specifically into OSPF area zero so that's how that plays out and then of like do is show that to you let's go ahead and me hide the screen for a moment and let me bring up an interface and I need to log back in and I let me do this I rearranged my screen but let me close window let me line this up again I was being clever and it bit me because I have to relock it all right my bad you bring this right over here fantastic in the password and right here we run router one so one router one will go into configuration actually you know what should do be first first before we configure OST F is we had a verified that it's not already running show IP protocols they'll show us we have any dynamic routing protocol is running we don't that's great so we'll go into configuration mode router OSPF will use process ID one lots of choices there and then I'm gonna set the router ID and on router one I'm gonna use 1 1 1 1 so it looks like an IP address it's a 32-bit address in binary so you can specify whatever you want the router ID to be looking like an IP address and then we'll go ahead and add our network statement so network 10.0.0.0 space and then we care about the first octet being a 10 and we don't care about the second octet don't care about the third octet what's there and don't care about the fourth octet space and then we'll put those into area 0 just like that now it's one thing to do a network statement and it's a totally separate thing to verify which interfaces are now in OSPF because of that network statement so a really quick easy trick is to show IP OS yeah interface brief and that will show us the interfaces that are now in part o or installed as part of OSPF so it got on router 1 gig 2 0 1 0 and gig 0 0 fantastic and it's in a wait state because those are all all three of those networks are Ethernet and so it's waiting to see whether or not there's a designated router on those segments and when it finds out there aren't any it'll win the election and it'll become the designated router here in about 15 to 20 seconds on each of those interfaces all right so that's router one let's go ahead and do the same thing for router two in our topology so I don't leave anybody behind now you bring back the images here so on router 2 we'll do the same thing we'll go into router OSPF create the process specify the router ID and we'll also tell it that any of its interfaces that begin with 10 should become part and participate in OSPF as part of area 0 so we'll go back to our interface and here we get a show IP protocols always a good idea to verify which router we're on make sure that not our product isn't already running like OSPF or something else because it's never a good idea to start configuring making changes than realizing oh no wrong device so here we have our two config T router OSPF one and we're gonna do a router ID of two - two - and then we'll specify a network statement Network 10 dot anything which is built like this and we'll pump those into area 0 and the verify that we'll do a show IP ospf interface brief just like that and we have a point-to-point link and we have the three others that are waiting but one of the wait too long on that one - slash 0 it's now a backup designated router so we have us a relationship if we do a well look at the neighbor who just show IP ospf neighbors and this is showing us from our 2's perspective it has a neighbor and that neighbor has the router ID of 1 1 1 1 and it's processes 1 and there are current state with that we have a full adjacency and this /dr says that that neighbor is the designated router for this network segment and that neighbors addressed that we're reaching them on is 10.12 dot 0 dot one and it's our local to slash 0 that we're using to reach him so that's right here I mean for the ten back up so effectively r2 says oh I see the neighbor relationship between myself and r1 over this interface right here and that's because they agreed they agreed on several things that are worth talking about here they agreed between them on this network segment they agreed on the actual network meaning oh that's the ten dot 12.0 network with the 24 bit mask they both agreed that between them that that network was in area zero fact I'll spell this out network 10.12 0.0 with the 24 bit mask they also agreed on hello and dead timers now you might say Keith what is what's a hold of time or how does that work well when these neighbors these neighbors care so much about each other that they are periodically gonna send hello messages back and forth across that link and they're expecting that those hold and dead timers have to match so by default on this type of network the hello interval is 10 seconds and the Delta H here for hello and the dead interval is 40 seconds and so if one of these routers doesn't see the others hello message and they don't see it within 40 seconds they're gonna assume that neighbor is dead no longer there and they'll have a little funeral and they'll move on with life you won't really he'll realize that neighbor is no longer there so that's what the hello and did they have to agree to on what those are gonna be and then the other thing is to to dr or not to dr they have to agree on that now let's talk for a moment about what a designated router is all about because this is a good discussion and let me use a slightly different color for that i use black so let's imagine that we have a network segment right here it's gonna put this off in isolation land right here for a moment so we have a network segment and on this network segment we've got many routers I'm gonna do a little overkill here but one two three four five six seven eight nine and we'll put 10 so we have 10 routers on this segment now Ethernet is broadcast based and these guys can all find each other dynamically it's all wonderful but if router 1 2 3 4 5 6 7 8 9 10 let's imagine that router 1 is going to build an adjacency a neighbor ship a full adjacency with our 6 and our 1 is gonna form a full of Jason see with our 7 and r8 and r9 and our 10 and r2 and r3 and r4 etc etc etc etc that's that's not so bad by itself for that one device to form all those adjacencies but if we do that also from every other device so 5 to 10 5 to 9 5 2 4 4 etc so we have a full mesh everybody has these full neighbor ships there buddy else that also is you know we could survive that the problem however is that once they have these neighbor ships what does it good neighbor do well a good neighbor lets you know when stuff happens and so if we have a change in the network every neighbors gonna have to tell every other neighbor about that change and the updates are just gonna be crazy we really don't need on an Ethernet segment like that that one segment we don't need to have 10 full adjacencies between those 10 routers it's just too much redundant overhead like yeah I heard about that from Joe yeah round 5 told me so what we do on on networks like this where we have multiple devices on the same network as we elect a dealer a designated router and you know what let's go ahead and put some personal terms let's imagine that we've got Mike and let's also go ahead and pick Gus so and let's imagine we have a roomful of 10 people now in this live stream we had a lot more than 10 but let's imagine we have 10 people in the room and Mike and Gus got there first and mike says hey I'm the first one here I don't see a clearinghouse for all these updates I'll become the designated router so it listens there's no other designated router becomes a designated router for this room this segment and then Gus shows up about 90 seconds later and says okay I'm willing to communicate I want to become neighbors and he says oh guy says Mike is already the designated router and because I showed up after he's already in place Gus becomes the backup designated router and they establish a full of Jason C so they are like like glue anything that happens they update each other life is good now what happens when the third one comes in the third device and I'll play that role when I show up on this network I jump in I powerup OSPF is now running I say oh oh I see these messages on this broadcast network I I see that we have a dr which is mike i see that we have a backup designated router which is Gus I'm gonna form a full adjacency with both of those guys because the designated router is like the clearinghouse for that network he's like the go-to guy by the way thanks Mike and then Gus if Mike goes away Gus is like the backup who if there's a problem on the network and Gus has to take over the route the role of Disney and router I also wanna have a relationship with them so at the moment we have full of Jason sees DRS fully adjacent with everybody the BD r which is Gus fully adjacent with everybody and me I'm not I'm not a dr or b dr they call me a dr other so if you see a router with the status of druther like dr other that's somebody who wasn't the dr wasn't the b dr but happy to be there and he's establishing relationship with both of them now here's where it gets interesting the fourth device comes in and some I don't know write this down so I forget and say the fourth device is Pat so Pat comes on the network has an interface on that network has been enabled for OSPF and Pat says hey okay what's going on the network oh I see we have a dr I see we have a b dr and what pat does he establishes a full of jason see with the dr which is my can data backup dr which is gus because that's the clearinghouse for any updates regarding that network segment they're gonna come from the dr and be dr and the be dr is there for backup purposes in case the dr goes away and then gus that then pat says lo la well we had this other guy here I see him this Keith he's not he's not the dr he's not the BTR he's a dr other and so he's aware of me and i'm aware of him and we will establish what's called a to a state it just says you know I know about Pat and Pat knows about me but we are not fully adjacent we're not gonna update each other because we're both getting updates from the designated router and that continues on as the fifth and sixth and seventh and eighth device comes in everybody establishes a full of Jason see with the DRM BDR and everybody else who's not idea or BTR addy or other are gonna form a to a state which is basically saying I mean I know about you you know about me it's all cool but we're not gonna do updates between us because we have the DRS in place okay so how does that affect a network type with OSPF and here's the answer to that question when we have an interface that is Ethernet the network um an Ethernet network we have 10 like say a five or six devices plugged into one VLAN if one device does a broadcast or sends a multicast everybody else on that same network segment it's going to be able to see it and that's considered a broadcast based network that's how Ethernet works it's broadcast based and so with OSPF if we enable OSPF by doing a network statement which implies also that the interface that has that IP address becomes part of OSPF if it's Ethernet the default network type is broadcast the default OSPF network type is broadcast for that interface and here's how that helps it helps because it says to everybody on that network segment and this device also hey this is a OSPF network type of broadcast that means that broadcast can be seen along with multicasts on this network segment and we're gonna have a designated router and i don't have to manually form my Jason sees I can send out broadcast and multicast messages more appropriate with OSPF and the neighbor ships will form octo magically we don't have to manually say he's the dr he's the BTR here's his priority we just enable OSPF and because the network i broadcast says yep allow the neighbor ships to form automatically and has default sets of timers so check this out what we just did by enabling OSPF on these ethernet interfaces we just locked in the hello and dead interval because it saw this Ethernet interface as a OSPF Network type of broadcast and it also identified that we don't have to manually assign neighbors because they'll dynamically find each other and we also identified because the network type of broadcast assumes that we're using a designated router these two routers are assuming that there needs to be a designated router and backup designated router for that Network statement so that's how the network statement the OSPF network type is assisting us with OSPF is because it takes the timers whether or not to use a designated router and it puts in a bunch of defaults for those based on the network type so in review if we have an OSPF router and it has an ethernet interface and we enable OSPF on it by default the OSPF network type is going to be broadcast which means the hello and dead interval timers are expected to be a certain value the OSPF is expecting that neighbors can be dynamically discovered and then if there's a broadcast or multicast sent it's going to be seen by every else on that network segment so and there's gonna be a dr on that segment that's all those things are meant by the type Network statement of broadcast and it's by on by default with ethernet so if we took a look at that let's do that now they go back to the screen hide that for a moment and let's take a look at this interface right here gig 2/0 on r2 that's this interface it's connecting from r2 over to our one so it'll bring up the interface I'll log back in and to see the actual interface type was a show IP ospf interface gig and 2/0 is the interface there's quite a bit of output but it's manageable so right here it's indicating that for that interface that the network type is broadcast again broadcast means okay here's the certain set of hello and dead interval timer and we can dynamically find each other neighbors we don't have to manually configure neighbors and the on this network we're going to be assuming that there's gonna be a designated router and BTR if there's more than one device there on that network segment and that's how it helps us and so if we looked at our ones good that head and do that on our one if we do i do show CDP neighbor so if I get the right interface so from our ones perspective the interface going over to our 2gig 1/0 and so we do they show IP ospf interface for gig 1/0 it would also show us that because it's Ethernet by default the OSPF network type is broadcast and as a result we're expecting to use DRS we're expecting hello and dead interval timers of a certain parameter and we're also expecting that we can dynamically discover each other and other devices on that same network because this broadcast based so that's what the OSPF network type of broadcast is all about alright so here's what I'd like to do next when might that be a problem that's what I'd like to talk about because that's where it gets interesting and dicey when would a network type of broadcast be a problem and I think I like to do is do some chalk talk with you and then we'll elaborate and say oh my gosh I can see why broadcast would not work in this scenario and that's why we have some other network types besides just broadcast for OSPF so let me go ahead and hide that and let me bring up a white Chuck word this one would probably work great yes it will all right this is me have fun this could be a fun fun dialogue here let me do that and they bring up one additional layer lots of bells and whistles okay so let's go ahead and take this Network here and we'll put some routers there you get the idea we have several routers and this is an Ethernet network now and the Ethernet network is considered a broadcast network and it's simply a broadcast network because if this device right here sends a broadcast or multicast into this network segment which of the other devices are going to be able to hear that the answer is all of them during the same VLAN same layer 2 network in the same layer 3 IP address so so we have the same IP subnet and it supports broadcasts and the hello intervals for OSPF on a broadcast network type is 10 second the dead is 40 so that's great so if we bring all the routers up we enable all those interfaces for OSPF by default on Ethernet it'll say this is a network type of broadcast and the factors of the hello and dead interval and the fact that the neighbors can be dynamically discovered all of that works so over here on the far left to keep it nice and simple I'm gonna put Network type OSPF and then I'll put here broadcast just like that alright and then I also need to prepare dynamic neighbors so that means is that these routers once the OSPF is enabled and they agree on the parameters they can dynamically discover and associate with each other life is good all right let me put a also on the OSPF Network type of broadcast we are going to be using designated routers and backup designated routers because that's how OSPF works on a broadcast network so let me go ahead and put a line there and I would like to UM I'm gonna go back in the time machine with you for a moment because this is where all this came from with the other alternate network types back in the 90s when I worked for Paramount Pictures a long time ago in a galaxy far away there was this new LAN technologies like in the early early days like in the 80s we used dedicated leased lines I worked for Blue Cross of California back then we had dedicated leased lines between Northern California and Southern California it was fascinating you know because we had that time division multiplexing on these t1 circuits a lot of fun stuff um but then this new thing came out called frame relay so it's a packet switched network and the frame relay you could just by logical circuits and you don't have to pay for the entire dedicated circuit so the cost was amazing also there's a lot more flexibility so frame relay about 20 years ago was the cat's meow and so we had situations with frame relay that might look like this so we have the headquarter sight and we'll call the headquarter router router one and then maybe have sites two and three and four and they hauled routers there as well and then for connectivity we would have Australia we would have connections like this and so with with the frame rail a cloud these would be representing pvcs permanent virtual circuits their identified with the datalink connection identifier on both sides and I got to tell you in in preparing for this today I thought all oh I get to go back in the time machine and I'll show how to do frame relay and I'll show him how to do dull sees and the mappings I thought myself stop the truck stop the truck Network types with OSPF a lot of the creative ones were built because of us because of frame relay however we we are gonna see very very little frame relay on any networks that have been around for a year or two or in a decade because frame relay is a very old technology now we have like Metro Ethernet and we have MPLS layer 3 VPN other SD way and all these other really cool options so just a little history on where this came from and you know 20 plus years ago frame relay was the king of the hill for LAN circuits but that brings us to this network Tech right here so if this is making a different color out here let's imagine that this represents Network 10 2000 slash and let's use a slash 29 that'll work so we use this last 29 and then these are all one one logical network but so the connections the PVCs would go from router 1 to router to router 1 to router 3 router 1 to router for now what I want to point out is that this would be referred to as a multi access network and so with this by the way you might say Keith what is a multi access network a multi access network is a network where the IP subnet can support more than just two people so if it's three or more if the network IP networks for three or more and the same subnet that can be considered a multi access network from the purposes of what we're discussing with OSPF so in this case here if I've got the headquarter site then off to the edges they've got you know site one network and then it's like two Network and site three network if this is just one network this is a multi access network but here's my question if router one sent a broadcast who would hear it so router one sends a broadcast or multicast in the case and also I want to point out in the case of when we're talking about OSPF we're talking about broadcast networks also consider that to be almost synonymous with multicast networks where that message would be received by everybody else on the network so if this headquarter router router one sent out a broadcast or multicast it would be seen by a router to router three router four I'm thinking home run yeah done got it that multicast that broadcast was seen by all the other devices no problem until we see about router two or out of three or router four and having them try to do a broadcast or multicast because I guess dicey then see if if router two sends out a broadcast or multicast into the network who's going to hear it because I'll tell you what router one is a router it is not a bridge it's not a switch it's a router so the problem here is that we have this multi access network but it does not support I put sub worked once again it does not support broadcast and what would we call something like this a multi access network that doesn't support broadcasts well there's a couple names we could think of it I can think of one like NB MA a non broadcast multi access network which is exactly what this is and in OSPF we have several ways of dealing with this one is an OSPF network type of non broadcast and let me tell you what that means so if we had a frame relay circuit which you're gonna be hard-pressed to find one these days but if you had a frame where they circuit and you had your dull C's and PVCs configure like this when you configure this interface here by default OSPF would say oh this is encapsulation frame relay and it would by default use a OSPF Network type when OSPF is enabled of non broadcast here's what non-broadcast means because we're still getting the same benefits as far as having an agreement between the devices non-broadcast means that we are still going to be using a dr and BDR and then we go ahead and spell that correctly shouldn't be too hard with a three-letter word so that's a yes yes so the broadcast network type uses a DRM BD are the non broadcast type uses the DRM BDR but here's the difference instead of having dynamic neighbors you have to do it manually and that involves going to the router process and manually specifying from router ones perspective my neighbor is and router too and my neighbor is and router three and my neighbor is and router four and you have to manually assign the neighbors so this is an example of where non-broadcast would be used and non broadcast in this sense basically means that the manual neighbors the neighbors ships would be saying manually and the hello and dead interval for the timers the default for those is thirty and I think it's three times that four times F four times yeah it's for me it's 120 we can check that for sure but so the non broadcast uses the dr a b dr it's expecting manual neighbor ships and the hello and dead interval timers changed a little bit but that's okay if router one or router two in around 300 or four all manually configuring neighbor ships the timers are all gonna match and life goes on no problem now for me and most people it is a pain have to set up these neighbor ships manually specify who your neighbors are and so cisco also has a solution for that and i will go ahead and put a little line right here and we're gonna use the same topology again so we still have this multi access network but we can use this network OSPF network type of point-to-multipoint and with a point-to-multipoint I hate to say it but this is the death I hear death of doctors and BTR's so anytime you have a network type that has the word point in it it's not a bad way to remember by the way if your network type has the word point in it point to multi-point point to multi-point non-broadcast point to point all by itself that means you're not you're no longer using a dr as cool if both devices are all the devices on the network segment say yep we're going to using point to multi-point none of them are expecting a designated router they all agree the timer's are gonna be associated as a same value with a point to multi-point and it's good to go so point to multi-point is a good option in this old frame relay configuration to avoid having to use a dr and have more of an agreement there's also some tricks that are going to be used as the leaf's the remote sites or used over here at the route sites advertised and forward information there's some next top trickery that goes on to make the actual packet flow work better that's beyond the scope of anybody that's not beyond the scope of most people who would care because we're not using frame relay anymore but that's another side benefit of point to multi-point so with point to multi-point no dr we have I don't change my color here back up a second didn't don't auto neighbors which means if you've got your own infrastructure set up correctly with the broadcast option on your daily on your PVCs that the neighbors will automatically be able to identify each other you don't have to manually assign the neighbors which is uh which is great so dynamic neighbor discovery the timers and the hello timer is 30 and the dead I think is four times thats i think that's 120 i we could just confirm that but whatever it is the same on both sides and that's fantastic and then and then somebody gave us it you know what I love it point-to-multipoint great except in my infrastructure my PVCs with this really old technology with frame relay my PVCs don't support the broadcast option so I really like the point-to-multipoint idea but they don't support this broadcast feature on each of the del C's for automatic discovery and Cisco said no problem we'll give you another option and that is point to multi-point non-broadcast it's like point to multi-point except you have to manually assign your neighbors just as you have to with non broadcast that's all it means so coming back here I will I'm gonna add the option right here in a bracket non broadcast and if we do not mount non-broadcast that means once again manual manual neighbors so you might think well you know now I'm not gonna go there you're never it's like really really likely you'll never ever ever ever ever ever have to do this but that I wanted to point out where this point-to-multipoint comes from it's if you have a non broadcast multi access network listening like ATM or PVCs with frame relay behind it the point-to-multipoint is a wonderful solution for that unless your PVCs don't support broadcast and then they have for the non broadcast option which says hey it's like the point it's like hey it's like point to multi-point except you have to manually add your neighbor statements once again but either any other case they don't use add ER now those are for those are for different OS PF Network types and the reason they come in handy is that several of the parameters are pre baked that both sides can understand like should we use the dr or not great it's decided if you're using the OSPF network type that's the same on both sides the timers are gonna be the same on both sides so whether or not you have to manually add the neighbor statements for OSPF depends on whether you're using a network type that says you have to or not so the non broadcast option when it shows up means you have to manually add your network neighbor statements for OSPF so there's one final network type I'm looking at the screen here that I want to chat with you about and that is point-to-point now a point-to-point network is not multi-access it's the only one of these that aren't so a point-to-point network that means there's two devices one here and one here and that's it so Ethernet you can have multiple devices on the same subnet that point-to-point that ap network is just two devices there's no room no options for anything else so how does your router know if a network segment is point-to-point the answer is it looks at the layer two encapsulation if the layer two encapsulation is Ethernet it says hey broadcast network for OSPF yeah that's right if it looks at the interface encapsulation on a serial link for example it says oh this is hdl-c or it's point-to-point protocol it's point-to-point and it defaults to IP ospf network type of a point-to-point now we can override those and there's not really a lot of great reasons to do so but we can actually go ahead and override those defaults for the network types but that's how it knows so let's take put in the last one here which is and I'll put a little line here point IP ospf network type of point-to-point and it would look something like this router one router two and then you have on this link now if this was a thern ette right here it would not be by default a point-to-point OSPF network type it would be broadcast so if this was a serial link and we are using encapsulation PPP on both sides or if we were using encapsulation hdl-c on both sides and if we went really way far back in the archives for frame relay we created a frame relay sub interface we can specify a point-to-point sub interface in frame relay but it's based on the encapsulation at layer two that's controlling what oh s PF network type is going to be so what I thought would be fun to do is let me see if I can find bunk bunk y yes I'm not too bad let's go ahead and let's take a limit let's configure the rest these routers routers three and four because we have this serial link and because this is using PPP I believe between them it'll automatically on this interface it'll show up as IP ospf network type of point-to-point and with point-to-point the hello hello and dead timers are set to 10 and 40 and they're not looking for a dr at all because it's a point-to-point so let's do that let me finish it around the horn and then we can take a look at the interfaces and if you want we can actually tweak and play with them and change them and and still make it work the OSPF network types do not have to agree as long as they agree enough I mean for example both sides if they're both sides have to agree whether or not there's gonna be a dr it's on that network segment that's one thing that has to be agreed upon and the timers have to agree but we could have like brought we could have broadcast and non broadcast on two different routers and then we can manually man we could we can manipulate the neighbor statements and make them work but you know what it's better just to understand how it helps us use the network types that are there and then move forward so let's configure those for a network so to do that let's go down here to this bad boy all right so just to remember where I am to show IP ospf and erase brief here on router one okay it's great look it's the dr for each of its ethernet segments because it was the first one up and it won and then here's our to show IP ospf interface brief great and show IP ospf neighbors great he's got a neighbor ship with r1 but not with anybody else in this because we haven't configured our three or r4 yet so let's go around the horn let's configure r3 just to remind you where that is r3 is this guy right here so we'll configure our 3G IP protocols nothing running yet show IP ospf nothing there right entity router OSD a router OSPF process ID one router ID three two three two three two three great and that work 10.000 and then wild card masks for the last three octets and will drop all of those into area zero just like that Wow I pressed dinner there we go come on you bad boy alright and wow that's it's not it's poking along there alright show IP ospf interface is free alright and let's do you read her floor as well so here on the router for config T and router OSPF one router ID 4.4.4 dot four and in our network statement it Wow okay it's gonna be the ten Network and then wildcard mask for the last three octaves because we want it's not gonna like that eight in there let me fix that control e to go to the end and put those into area zero alright and a quick check the show IP ospf interface brief yeah we got a new neighbor ship with our two fantastic and new neighbor ship with our three that's fantastic and then we did a show IP ospf neighbors and that should show us neighbor ships I'm thinking with we're on our four oh yeah with r2 and r3 fantastic alright let's go over to our three and just so we know where we are on the topology this is our three right here and I'm expecting on this serial interface serial 3/3 I'm expecting that interface type to be IP ospf Network type of point-to-point and that's because of the encapsulation that's on that serial interface that's the whole reason so if we go up to that and we do a I'm on the right router show IP yeah show IP ospf interface for having some serious lag problems not sure what it is all right show IP ospf interface serial 3/3 and survey says all right so here's the command is you'd fantabulous and right here it's showing that the network type is point-to-point and for that let's take a look at the interface encapsulation show interface serial 3/3 oh my gosh I have no idea why this is lagging so bad oh there we go maybe knows I'm doing a don't ok so there's just the raw output from show interface serial 3/3 and the encapsulation is PPP so that's the reason from an OSPF perspective that it used the OSPF network type of point-to-point so if we wanted to change any of these we could go to configuration mode interface serial 3/3 and type in IP ospf network and then do a question mark we have the options for broadcast which uses the dr we have non broadcast which doesn't use a dr you have to manually specify your neighbors we have point-to-point which doesn't use a dr we have point-to-multipoint which doesn't use a dr and then if we do point to multi-point there's also a following option of non broadcast which means we would also have to manually specify our neighbors for OSPF in that interface if he's the point to multi-point non broadcast which is v OSPF network type that we've talked about all right let me see if that's everything i wanted to talk about with you the major the major focus and today's session was to take a look at what our OSPF network types and we have identified five of them four three three of them two or three of them you probably never ever ever have to use and also what the benefit is and the big benefit is that there are some defaults in place on Ethernet it's going to be a broadcast network type on hdl-c or PPP serial link is going to default to a network type of point-to-point and the benefit of each of those is there's pre agreements on whether or not we're going to use a dr or not there's pre agreements on what the timers are going to be for the hello and did intervals and so then we just have to get the other parameters correct like the network length and the area that the network is in and authentication and a few other details just to make sure that OSPF will then form the adjacencies and if it's just a dr and a b dr they'll form full of Jason sees the third device in will also form full of Jason C's but that fourth device in will not form a full adjacency with the other D or other but it will form a Jason sees with the dr and the b dr which were happily played by Mike and Gus in this analogy so that's that's what I wanted to cover today and there is a lot to oh s PF but I I wanted to focus on again what is a network type for OSPF what are some of the defaults for it and how does it help us and I think we did that as well so you know what let me let me do this I haven't had even just a moment to look at the Q I appreciate a lot of people helping each other with questions and answers I'm gonna put some music on just for maybe I'm one minute I may be a minute 10 seconds and I'm gonna take a quick look at the Q see if there's any burning questions you want me to elaborate on if you do have a question you like me to ask if you want to retype it in that way to be right there near the bottom so I can see it and I'll be back in just a moment for with your questions meanwhile some music [Music] [Music] [Music] [Music] [Music] [Music] all right and some great questions and that some great answers from the group so thank you for that one of the concepts are all the the clarifications was multicast and now when OSPF is speaking and they're doing their discovery and adjacent sees and so forth if we're on a network like a broadcast network or on a network that like point-to-multipoint that supports multicast them and i say a broadcast that's a frame that sent from one device that can reach everybody else the exception that is point-to-multipoint we're like a hub-and-spoke topology multicast is used local multicast for those interactions so if we have Mike and Gus which are the d r and b dr as we're sending information to them as dr others we're sending it to the multicast address up to 2400 six and as we communicate with all oh s PF speakers not DRS and not B DRS we send it to to 2400 five so if you have networks that are that are not non-broadcast they are using those multicast addresses so on point-to-point links if we are to do the protocol analyzer we would see a lot of traffic seeing sent back and forth two to 2400 five now a to 2400 address is local it doesn't get routed off the local network so with IP multicast amande bootstrap routers and all that good stuff we can actually route traffic streams across networks with using like rendezvous points and using run and PIM protocol in a minute multicast no sure oh I had a problem with that but that's not what we're talking about with OSPF we're talking about you know OSPF does use a multicast address but when they send out a multicast based on the type of network it's the question will that multicast reach everybody and so on broadcast networks and point-to-multipoint those are seen and and point-to-point we just shoot them back and forth over that link there was one other question that I oh yeah yeah yeah so great the only weather christians was when would be what's a real world application freeze like a point-to-multipoint non-broadcast option and that is if you have to it only if you have to so we don't have a lot of frame relay point-to-multipoint networks going in anymore i mean there's just better options that service providers have for us they give you a an Ethernet circuits a here is it great and then they do MPLS for you with layer 3 VPN s to connect your sites together so the whole conversation about frame relay really goes back to 20 years ago and there's not too much of an application for it anymore because we don't use those technologies anymore those are band-aids and solutions in the days when we had one device that had at the headquarter site with multiple PVCs going to remote sites when would we ever use Brock so broadcast is a great solution for Ethernet if we ever if we ever wanted to manually have to manually specify who our neighbors were we could force everything the non broadcast that would work but we didn't have to manually assign our neighbors which is not fun so the two main ones we're gonna use today most the time are broadcast based on Ethernet and we're done and then if they have a service provider doing MPLS Leo three VPNs for us we just shoot our traffic over Ethernet and again we may peer with our service provider using OSPF but it won't be anything tricky it'll be like one neighbor the the service provider at the edge their provider edge and we're talking to them so a great great question okay I noticed in my a few years back that the BBU are always selected first before d/dr hmm you know I've never seen that ever so I mean at the end of the day if you have only one device it's gonna be a dr and then the second device comes up and it'll be the b dr and they're never gonna supersede each other as long as that d are still in place and if you have two devices that come up at the exact same moment the interfaces have a default priority and that default priority is one so if you have two devices that both come up at the same moment they both have the same priority of one each they won't the higher router ID is going to go ahead and win and it'll become the dr for the segment the other guy be the DB dr and then every else was just falling after that another question i saw here was submitting saturdays and the answer is yes it is Wednesday today Thursday Friday in three days I haven't put the outline - I've taught something many many many times and I love it so I'm going to put together subnetting Saturdays for probably a month and a half fairly short chunks that somebody can just take in order and just ease into the idea first of all what is an IP network address and what is the mast do and then the binary behind that and then why would we need to submit and then how to subnet gracefully and I'm gonna teach the finger game because worldwide it is loved and it's easy so if you're not the kind of guy says I love anything ^ 0 in fact I love powers of two you don't need to worry about it I teach you how to do it without having to do powers of two or realize what two to the power of zero is and why is it always 1 and yeah I built that finger game and the ability to calculate correctly subnetting based on my lack of math skills frankly I I'm not good at I'm not great at math I mean I have a high school education I do whoo-ahh that's five years of my life but yeah when I I learned subnetting back in the 80s and I loved it and I thought to myself as I start to teach to other people I thought we need a way that people can just understand this you know nice easy steps nothing mystical or magical use your fingers occasionally to count and calculate what the correct subnets are and that's starting it would be 11:00 a.m. Pacific time on Saturdays starting this Saturday no the good news is I built a playlist and it is ogi t original gangster by T dot online I had to think about that for a second / sloth thanks mister sloth I thought that's a really easy way to find it and that's gonna be plastered everywhere self yet and I'll add these live streams in the right order into that playlist so if you're like a couple months from now you're thinking ah what's new or what they're just go to that playlist go down the list say oh that looks new and that lets new and I want to read brush up on that and so forth also if you haven't already you know sometimes we get involved in these live streams and I forget to invite you if you haven't already take a moment now and subscribe that way you can get alerts and notifications when new stuff comes out hit the bell so you can become part of the family and and learn alongside of us alright I think that's almost all of it and Johnny quad I love my IP calculator too alright hey everybody thanks for joining me I'm gonna cut this off right now it's been just under an hour I really appreciate the participation and the answering of questions I believe anybody who wants to can apply themselves and not only get a CCNA but also learn the skills regarding a CCNA so when you walk into a job environment and they're asking you to troubleshoot which is a big part of IT work today you can say yeah I understand how this works I have hands-on experience doing that and based on x and y and z oh there's your problem right there and just solve it and be part of a team that may be involved in solving it because it could be application layer stuff and networking stuff and having people that can communicate and come together makes makes for a very happy team that's successful all right I'm gonna go out with some exit music so let me find that real quick here it is got it and I look forward to seeing you in our very next stream and in the playlist and until then be well thanks for being here [Music] [Music] [Applause] [Music] [Music] [Music]

Channel: Keith Barker

Views: 19,360

Rating: 4.9502664 out of 5

Keywords: ccna, ccna 200-301, ccna certification, ccna study, ccna training, cisco, cisco ccna, cisco certifications, cisco training, new ccna, new ccna 2020, new ccna 200-301, networkchuck ccna, networkchuck, ospf network types, ospf networking, open shortest path first, cisco routing, open shortest path first protocol, how ospf works, link-state protocol, ospf routing protocol, ospf network types explained, ospf network types dr bdr, ospf nbma network types

Id: E-MYwBJrMMI

Length: 60min 42sec (3642 seconds)

Published: Wed Jan 08 2020