Hello, my name is Tyler Mcmann with Aruba Networks and this is part three of the networking essentials course where we're going to be learning about routing protocols. In a previous video, we talked about static routing and established in our labs a static route to add our foreign destinations. So being able to ping all the way from PC one to PC four across different VLANs using multiple gateways, great. In this video, we're actually going to dive in to a dynamic routing protocol, we're going to learn about how routing protocols can be broken down. And what are the different protocols that are supported in an enterprise switching operating system such as Aruba CX. And ultimately the ins and outs of open shortest path first, so sit tight, and let's jump on in. [MUSIC] All right so routing protocols could be broken down in I guess two main ways, you could look at them as inside your interior network, your internal corporate structure if you will. And then the routing protocols that are used between big service providers and large corporations. With interior there are a number of protocols that we can choose from. With exterior, there's really just a single protocol that's used out there known as Border Gateway Protocol. It's a beast of a protocol but it is been used to route the entire Internet for quite a while. With routes above 800,000 as of my last check, 815, maybe 900,000 routes right around there. So a huge, huge application to run, which is available on the CX operating system. When we are trying to connect out with a large corporate edge routing service. For us though, we're not going to focus on that, we're going to look at some of the interior gateway protocol options that we have and what we can use in our own internal network. Within CX, the main supported route types you're going to see are the local IP addresses assigned to the router itself, or the switch, or whatever layer three interface you're using. Those will have a subnet mask which indicates the connected route that they are within. So in our example where we had VLAN 99, we went under the interface and we assign the address 172.16.99.101. Now because we did a slash 24, that indicated the first 24 bits are the networking portion. And the last eight bits out of 32 total with IPV4 give us a range of anywhere from .0 all the way to .255, we've been over this before, but it's worth reiterating. You can use any address from .1 to 254 because we reserve the very first and the very last addres that's available in that 256 address range, indicated by the 8 bits or the host bits that you see here. On top of that though, we have our destinations that we can go to, not just the connected ones like these, but static routes indicating whatever destination you want or even a default route that you want to add. Those are all ones that [COUGH] essentially you're popping in yourself. You're putting those in as administratively configured routes, as indicated on the interface or as indicated in global config. Dynamic routing protocols start here with RIPv2, OSPF, and Border Gateway Protocol. RIPv2 or routing information protocol has been around the longest. It is very simple but it is also fairly limited and it's a bit dated, it is very slow, so it can take 180 seconds for a hold down timer to expire on a route, meaning you could have three minutes before your router realizes it can't reach that destination. With OSPF that tightens up quite a bit to about 40 seconds depending on how you have it set up. And you could actually lower that even less or even sub second by doing a little bit of tuning and tweaking. Open Shortest Path First, this is going to be the protocol that we're going to focus on in this course. And then BGP is kind of the complete opposite of RIP, BGP is our external gateway protocol choice and it scales to millions of routes, literally. So if you were to figure an address or either the physical port or for a switch virtual interface, then you can go in under the port or the interface and enable routing. And enable the layer three address that you want to use, then validate with a show ip route. All of these we demonstrated in the last video, so it's worth a review if you want to check that one out. So with static routing, we talked about this earlier, not really scalable, but it does have an advantage and that's very quick, very simple, very easy to kind of punch in there and update your routing table. Dynamic routes, you don't have to update the routing table. You just simply enable the route or the dynamic routing protocol. And if your neighbor runs that same protocol, they'll automatically form a neighbor adjacency with OSPF or RIP with any interior gateway protocol. From there, the protocol itself like OSPF will update your routing table for you. It will advertise all your connected routes to all your neighbors, they'll advertise all their connected routes to you. And before you know it, you have an entire link state database of all possible routes within your interior gateway or within your area that you're routing for. So let's take a look at OSPFv2 and the basic steps of setting it up. This has been around for a long time as well. It is a very scalable routing protocol. It's what we would call link state because you're sharing the state of your links, your connected links with your neighbors. And with that you can build a large topology or link state database that shared among all your other neighbors that you are also running OSPF with. Before you get to the Internet, all your routes inside your local area network or inside your what we call an autonomous system your enterprise of networking will automatically kind of converge. In which case you've just enabled OSPF, maybe you've identified the router to its neighbors by a IP address called the router ID. And then it will automatically start establishing Hello messages for you to configure. We may or may not get into passive interfaces, there's like I said, it's been around for a long time. So there were a number, a number of different ways that you can tune and tweak the performance of OSPF. But in this case, we're just going to look at the basic setup to get it up and running that you can apply anywhere. The other big advantage of OSPF besides it being scalable and actually pretty easy to just get up and running is that it is standardized. It's in a request for comments which is that other organizations have worked with each other to submit improvements to the standard over the years. So this IETF standard, you can easily look online and read everything about this standard. Any router, vendor can support OSPF. And because it is standardized, most routing vendors do. What that means is that you can have a OSPF process running on your CX switch, you can have a separate switch that is from some other third party vendor. And in all likelihood they'd still be able to exchange OSPF routes with each other. So when you enable OSPF, you indicate which interfaces that you are going to be routing for. Your neighbors do the same thing, they enable OSPF and their links, OSPF and their links, and then they do an exchange once they establish their adjacencies, they form neighbors, basically. And with that exchange, they agree upon an entire OSPF topology where everybody knows the speeds and the cost of using a particular path versus another. And this helps OSPF determine the best path or correct any path changes. In the event that you have a an outage or a link goes down, your traffic is able to route around automatically. This is a huge benefit of dynamic routing protocols versus you just statically saying this is the path I want to use if your topology changes. If a router goes down, if a better route shows up, you as the administrator have to actually make the change in the command line. Whereas with OSPF that change can be applied by default within 40 seconds. Under OSPF here, the general operation Phase one after you enable OSPF is you start establishing neighbor adjacencies with other routers that are also running OSPF. This is actually done through a multicast exchange, meaning that it will automatically exchange messages specifically to an address that only other OSPF routers are listening to. Once that exchange of information, your neighbor adjacency is established. And you start this exchange, you'll build a complete topology of all routes that not only you know about, but all routes that your neighbors knew about or know about as well. So inside your company inside or your design here, inside your area is what we'll call it. All of your OSPF routes are shared with everybody else building your link stay database or your topology. From there, OSPF runs an algorithm to determine the best path by taking the costs of every link along every possible path and determining what is the shortest path based upon that cost value. So the faster the link, the faster your band width, the lower the cost for traffic to pass over it. The best route is the one that ultimately ends up in the routing table. To validate you do show IP route. There's the destination and there's the next hop to reach that destination. OSPF ends up being the method that was used to inject that route into your routing table. If you remember in the previous lab, we were doing static routes, so it was thrown, our routes were put in with static at the end, and because we, statically typed them in. It's really not that, difficult, you can go in and tweak this. You can apply costs, you can change the network values, you can make interfaces passive, you'll still advertise them, but you won't send out Hellos on them or receive Hellos. And there are reasons when you start expanding your network, you might make some of these changes for efficiency sake or for security reasons. But in our case, the only things that are absolutely required is you enable the process, you set your area ID. And then under each of your interfaces that you want to advertise or form adjacencies, you put in your IP OSPF process ID, the command area and the area ID of zero, and that's it. Not very difficult. So we're going to pause there and stop this video. And the next video, the last video we're going to go through and to finish our lab and change from a static routing solution to a dynamic routing solution and actually see OSPF. So I want to thank you guys for your time and I'll see you guys in the next video.
