1 00:00:00,860 --> 00:00:06,800 The third category of routing protocols is advanced distance vector. 2 00:00:06,870 --> 00:00:15,890 In theory, EIGRPP or enhanced interior gateway routing protocol takes the best of both distance vector 3 00:00:16,460 --> 00:00:22,310 and link states routing protocols and combines that into a single routing protocol. 4 00:00:22,640 --> 00:00:30,310 You may see that EIGRP is described as a hybrid routing protocol where it combines elements of both 5 00:00:30,320 --> 00:00:36,440 distance-vector and link-state into a single routing protocol that isn't entirely true 6 00:00:36,500 --> 00:00:41,710 and in the EIGRP videos, we'll discuss that in a lot more detail. 7 00:00:41,750 --> 00:00:48,370 In theory, EIGRP takes the best of distance vector in that it's very easy to configure. 8 00:00:48,380 --> 00:00:55,370 You could configure EIGRP on a router as an example by using just two commands and thus it's very 9 00:00:55,370 --> 00:01:01,340 easy to configure in the same way that RIP in the past was easier to configure. 10 00:01:01,490 --> 00:01:08,540 EIGRP however forms neighbor relationships in a similar way to link-state routing protocols such as 11 00:01:08,540 --> 00:01:09,670 OSPF. 12 00:01:09,740 --> 00:01:18,170 So unlike distance-vector routing protocols like RIP that do not form neighbor relationships, EIGRP does 13 00:01:18,290 --> 00:01:20,440 form neighbor relationships. 14 00:01:20,570 --> 00:01:27,680 So in theory it's taking the best of both distance factor and link-state and combining them into a single 15 00:01:27,680 --> 00:01:34,520 routing protocol that gives you the power of a link-state routing protocol with the ease of configuration 16 00:01:34,850 --> 00:01:37,520 of a distance vector routing protocol. 17 00:01:37,520 --> 00:01:42,440 The disadvantage of EIGRP is that it's Cisco proprietary. 18 00:01:42,440 --> 00:01:49,580 So unless you are running a pure Cisco network you may have to choose a different routing protocol such 19 00:01:49,580 --> 00:01:51,040 as OSPF. 20 00:01:51,050 --> 00:01:56,510 If however, all your devices are Cisco devices EIGRP is a very good choice. 21 00:01:56,780 --> 00:01:59,030 It's very easy to configure. 22 00:01:59,180 --> 00:02:00,920 It's very quiet. 23 00:02:00,920 --> 00:02:08,900 It updates very quickly and is a good choice for most enterprise networks that only have Cisco devices. 24 00:02:10,210 --> 00:02:18,580 Another very important concept to understand is administrative distance which is essentially the believability 25 00:02:18,580 --> 00:02:25,270 factor of a route. When multiple routing protocols are configured on a router and are trying to put 26 00:02:25,270 --> 00:02:28,870 routes into what's called the routing information base or RIB 27 00:02:28,990 --> 00:02:34,740 also called the routing table a router will need to decide who to believe. 28 00:02:34,990 --> 00:02:42,620 If OSPF says go left and EIGRP says go right to get to a network which writing protocol 29 00:02:42,670 --> 00:02:44,120 does the router believe 30 00:02:44,260 --> 00:02:47,520 and which route does it insert into the routing table? 31 00:02:47,770 --> 00:02:54,880 In other words, what is the trustworthiness or believability of the routing information that the router is 32 00:02:54,880 --> 00:03:03,740 receiving? Administrative distance is then used as a tiebreaker to determine which way to go when multiple 33 00:03:03,740 --> 00:03:07,560 routing protocols tell the router to go different ways. 34 00:03:07,700 --> 00:03:14,730 As an analogy, administrative distance is used as a tiebreaker to determine which way to forward traffic. 35 00:03:14,990 --> 00:03:21,620 If OSPF says go left and EIGRP says go right the router uses administrative distance to determine 36 00:03:21,620 --> 00:03:29,840 which routing protocol it believes most. Technically what happens is that the routing protocol with the 37 00:03:29,840 --> 00:03:33,640 lowest administrative distance is more believable 38 00:03:33,770 --> 00:03:39,830 and its routing information is inserted into the RIB or routing information base or routing table 39 00:03:40,280 --> 00:03:46,230 in preference of other routing protocols that have a higher administrative distance. 40 00:03:46,370 --> 00:03:55,220 So EIGRP has a lower administrative distance than OSPF, EIGRP has an administered distance of 90 OSPF 41 00:03:55,250 --> 00:03:57,570 has an administrative distance of 110. 42 00:03:57,690 --> 00:04:06,920 So internal EIGRP would be preferred over OSPF so the lower the administrative distance the more 43 00:04:06,920 --> 00:04:09,820 believable a routing protocol is. 44 00:04:10,040 --> 00:04:12,590 You cannot believe anyone more than yourself. 45 00:04:12,590 --> 00:04:21,260 So a router will believe routes that it originates above routes received from neighboring devices a directly 46 00:04:21,260 --> 00:04:28,700 connected interface has a believability factor or administrative distance of 0 a static route configured 47 00:04:28,760 --> 00:04:36,410 to a next-hop IP address has a administrative distance of 1 when a static route is configured to a directly 48 00:04:36,410 --> 00:04:44,300 connected interface it is deemed to be directly connected and therefore has a believability factor or 49 00:04:44,300 --> 00:04:46,890 administrative distance of 0. 50 00:04:46,910 --> 00:04:52,640 The reason why static routes have such a low administrative distance is that the router believes that 51 00:04:52,670 --> 00:05:00,620 you know more than other routers do you as the administrator are supposed to know what you are doing 52 00:05:01,040 --> 00:05:07,940 and thus the router believes you more than it believes routes received via routing protocols such as 53 00:05:07,940 --> 00:05:10,510 OSPF and EIGRP. 54 00:05:10,910 --> 00:05:15,670 EIGRP has an administrative distance of 90 for internal routes. 55 00:05:15,800 --> 00:05:24,320 Those are routes that originated in EIGRP and were not redistributed or taken from a different routing 56 00:05:24,320 --> 00:05:33,470 protocol and then put into EIGRP. OSPF has an administrative distance of 110, RIP has an administrative distance of 120 57 00:05:33,950 --> 00:05:38,170 and unknown routes have an administrative distance of 255. 58 00:05:38,450 --> 00:05:46,450 As you can see EIGRP has a lower administrative distance than RIP does and that's because EIGRP 59 00:05:46,460 --> 00:05:50,380 is a better or more powerful routing protocol. 60 00:05:50,580 --> 00:05:58,280 EIGRP will take bandwidth and delay into account when determining the best route, RIP only uses hop 61 00:05:58,280 --> 00:05:59,140 count. 62 00:05:59,150 --> 00:06:05,770 So EIGRP seemed to be better than OSPF which is better than RIP.