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These are the user uploaded subtitles that are being translated: 1 00:00:00,000 --> 00:00:05,000 align:middle line:84% Link state routing protocols have greater visibility of the network 2 00:00:05,000 --> 00:00:10,000 align:middle line:84% and are generally more powerful than distance vector routing protocols. 3 00:00:10,000 --> 00:00:14,000 align:middle line:84% As an example, OSPF is a more powerful routing protocol than RIP. 4 00:00:14,000 --> 00:00:18,000 align:middle line:84% Links state routing protocols, to use our analogy once again 5 00:00:18,000 --> 00:00:23,000 align:middle line:84% have a road map or a map of the entire network. 6 00:00:23,000 --> 00:00:26,000 align:middle line:84% They can thus make better routing decisions 7 00:00:26,000 --> 00:00:31,000 align:middle line:84% than distance vector routing protocols which only have a road sign. 8 00:00:31,000 --> 00:00:36,000 align:middle line:84% So rather than just looking at the road sign that says go left 9 00:00:36,000 --> 00:00:39,000 align:middle line:84% and your city is a 100 miles away 10 00:00:39,000 --> 00:00:43,000 align:middle line:84% and then drive a 100 miles to get to your city. 11 00:00:43,000 --> 00:00:47,000 align:middle line:84% A router running link state routing protocols has a road map 12 00:00:47,000 --> 00:00:51,000 align:middle line:84% and thus has better visibility of the network or topology. 13 00:00:51,000 --> 00:00:54,000 align:middle line:84% Link state routing protocols will flood the network 14 00:00:54,000 --> 00:00:59,000 align:middle line:84% with what are called LSAs or Links State Advertisements 15 00:00:59,000 --> 00:01:03,000 align:middle line:84% this information is flooded through the entire network 16 00:01:03,000 --> 00:01:05,000 align:middle line:84% if routers are configured in a single area 17 00:01:05,000 --> 00:01:11,000 align:middle line:84% or are flooded within the area when special areas are created. 18 00:01:11,000 --> 00:01:14,000 align:middle line:84% Does information about the entire network 19 00:01:14,000 --> 00:01:21,000 align:middle line:84% or area is received by all routers in that network or area. 20 00:01:21,000 --> 00:01:26,000 align:middle line:84% the LSAs are propagated between all routers without being changed 21 00:01:26,000 --> 00:01:30,000 align:middle line:84% all routers will individually create or populate 22 00:01:30,000 --> 00:01:34,000 align:middle line:84% what’s called a topological database which is a database 23 00:01:34,000 --> 00:01:38,000 align:middle line:84% that’s the same on all routers within an area 24 00:01:38,000 --> 00:01:44,000 align:middle line:84% or once again if running only a single area, all routers within the network. 25 00:01:44,000 --> 00:01:48,000 align:middle line:84% The topological database contains information about 26 00:01:48,000 --> 00:01:51,000 align:middle line:84% all routers within that area or network. 27 00:01:51,000 --> 00:01:57,000 align:middle line:84% All the links to those routers as well as the states of those links 28 00:01:57,000 --> 00:02:04,000 align:middle line:84% hence the term link state routing protocol is the link up or is the link down? 29 00:02:04,000 --> 00:02:08,000 align:middle line:84% So router 1 as an example will tell all routers 30 00:02:08,000 --> 00:02:15,000 align:middle line:84% within the area about the links connected to it and the state of those links. 31 00:02:15,000 --> 00:02:17,000 align:middle line:84% Are they up or are they down? 32 00:02:17,000 --> 00:02:20,000 align:middle line:84% the routers run what’s called 33 00:02:20,000 --> 00:02:24,000 align:middle line:84% the shortest path first algorithm or SPF algorithm 34 00:02:24,000 --> 00:02:29,000 align:middle line:84% OSPF, as an example, is Open Shortest Path First 35 00:02:29,000 --> 00:02:35,000 align:middle line:84% or in other words, it’s an open standard that runs the SPF algorithm. 36 00:02:35,000 --> 00:02:41,000 align:middle line:84% Open Shortest Path First or OSPF, when the routers run the SPF algorithm 37 00:02:41,000 --> 00:02:46,000 align:middle line:84% they put themselves at the root of an SPF tree 38 00:02:46,000 --> 00:02:49,000 align:middle line:84% and then calculate or workout 39 00:02:49,000 --> 00:02:54,000 align:middle line:84% the best route to destination networks from their perspective. 40 00:02:54,000 --> 00:03:00,000 align:middle line:84% a routers perspective will vary depending on where it is in the network topology 41 00:03:00,000 --> 00:03:03,000 align:middle line:84% and thus the best route for 1 router 42 00:03:03,000 --> 00:03:06,000 align:middle line:84% maybe different to the best route for another router. 43 00:03:06,000 --> 00:03:10,000 align:middle line:84% The router essentially determine the best route for themselves 44 00:03:10,000 --> 00:03:15,000 align:middle line:84% by running the SPF algorithm against the topological database 45 00:03:15,000 --> 00:03:20,000 align:middle line:84% and then they put the best routes into their local routing tables. 46 00:03:20,000 --> 00:03:26,000 align:middle line:84% examples once again of link state routing protocols include OSPF 47 00:03:26,000 --> 00:03:31,000 align:middle line:84% or Open Shortest Path First and ISIS or Intermediate System-Intermediate System. 5682