1 00:00:08,260 --> 00:00:14,220 So in the previous few videos, I talked about one dynamic way of routers 2 00:00:14,220 --> 00:00:18,560 to dynamically learn about who the rendezvous point is for any given group. 3 00:00:18,560 --> 00:00:22,520 That was the Cisco proprietary auto RP feature. 4 00:00:22,520 --> 00:00:25,460 Now I'm going to introduce our last topic in a series of videos, which 5 00:00:25,460 --> 00:00:28,300 is the PIM bootstrap router. 6 00:00:28,300 --> 00:00:31,880 And let's do some comparisons between the two. 7 00:00:31,880 --> 00:00:38,240 So there are some similarities between the PIM BSR and the auto RP features. 8 00:00:38,240 --> 00:00:42,020 By the way, BSR stands for bootstrap router. 9 00:00:42,020 --> 00:00:47,180 So both of them provide dynamic discovery of PIM rendezvous points. 10 00:00:47,180 --> 00:00:51,740 In both protocols, we have candidate RP's announcing their capability 11 00:00:51,740 --> 00:00:59,640 to be the RP for the PIM BSR. 12 00:00:59,640 --> 00:01:03,580 We actually have a router called the bootstrap router that's a role that 13 00:01:03,580 --> 00:01:07,520 a router plays who transmits messages that allow other routers to learn 14 00:01:07,520 --> 00:01:09,120 of potential RP. 15 00:01:09,120 --> 00:01:14,500 So this is kind of like the role that the mapping agent played in auto 16 00:01:14,500 --> 00:01:18,300 RP. But there are some very big differences between them. 17 00:01:18,300 --> 00:01:23,500 Number one, PIM BSR is an IETF standard. 18 00:01:23,500 --> 00:01:28,360 As a matter of fact, if you go all the way back to the original PIM specification, 19 00:01:28,360 --> 00:01:35,440 RFC 2117, that was the very first RFC for PIM sparse mode. 20 00:01:35,440 --> 00:01:38,860 Even in there, it talked about a bootstrap router and the process for 21 00:01:38,860 --> 00:01:42,560 doing that. So this has been around for a while. 22 00:01:42,560 --> 00:01:47,700 But it really came into its own when PIM version 2 came out. 23 00:01:47,700 --> 00:01:52,040 So the current RFC for this is RFC 5059. 24 00:01:52,040 --> 00:01:55,620 And like we said, auto RP Cisco proprietary. 25 00:01:55,620 --> 00:02:01,240 So PIM BSR really was developed for PIM version 2. 26 00:02:01,240 --> 00:02:04,780 Chances are probably not going to run across too many devices these days 27 00:02:04,780 --> 00:02:07,620 running PIM version 1, so that's not going to be a problem. 28 00:02:07,620 --> 00:02:12,940 But only works for PIM version 2, whereas auto RP works for either version 29 00:02:12,940 --> 00:02:17,760 of PIM, if that's a concern for you. 30 00:02:17,760 --> 00:02:23,620 And PIM BSR, one of the things you lose is the ability to define the scope. 31 00:02:23,620 --> 00:02:27,920 Remember with auto RP, when you were configuring your router as an RP 32 00:02:27,920 --> 00:02:32,380 candidate, one of the things you had to put in in the command was the 33 00:02:32,380 --> 00:02:38,860 scope. And that gave you the ability to control the TTL of those RP announced 34 00:02:38,860 --> 00:02:41,660 messages that the candidate RP's were sending. 35 00:02:41,660 --> 00:02:45,640 So in that way, you could say, all right, well, I only want this guy to 36 00:02:45,640 --> 00:02:51,600 be the RP so far into the network by limiting how far away his messages 37 00:02:51,600 --> 00:02:58,060 can go. With PIM BSR, that's not an ability that you can control. 38 00:02:58,060 --> 00:03:02,400 Few more differences. 39 00:03:02,400 --> 00:03:07,560 One of the big benefits of the BSR is not only is it an IETF standard, 40 00:03:07,560 --> 00:03:09,740 but you can do away with dense mode. 41 00:03:09,740 --> 00:03:13,780 Remember how with PIM sparse dense mode, which is what we needed for auto 42 00:03:13,780 --> 00:03:19,180 RP, we had all these risks of multicast streams possibly being flooded 43 00:03:19,180 --> 00:03:23,200 in dense mode if there was no rendezvous point to handle them. 44 00:03:23,200 --> 00:03:25,880 And there were certain ways we could get around that like the sync RP 45 00:03:25,880 --> 00:03:29,040 and stuff. But here, you don't have to worry about that. 46 00:03:29,040 --> 00:03:31,240 Every single interface can be in sparse mode. 47 00:03:31,240 --> 00:03:34,820 Don't have to worry about the possible risk of flooding of multi multicast 48 00:03:34,820 --> 00:03:43,320 traffic. Also, in auto RP, the device that was responsible for sending 49 00:03:43,320 --> 00:03:46,120 the messages to everybody saying, okay, here's your list of rendezvous 50 00:03:46,120 --> 00:03:47,900 points was called the mapping agent. 51 00:03:47,900 --> 00:03:51,640 And we said, you could have for redundancy two or three or four mapping 52 00:03:51,640 --> 00:03:56,860 agents as long as the messages they were sending out were identical. 53 00:03:56,860 --> 00:04:00,340 Well, in PIM BSR, there's only one BSR. 54 00:04:00,340 --> 00:04:03,440 And that is elected from candidate BSRs. 55 00:04:03,440 --> 00:04:08,740 So you still have your redundancy there, but there's only one bootstrap 56 00:04:08,740 --> 00:04:13,240 message being sent out from the BSR router itself. 57 00:04:13,240 --> 00:04:20,380 Another difference with auto RP, auto RP had some reserved addresses. 58 00:04:20,380 --> 00:04:25,500 We see them here, 2240139 and 2240140. 59 00:04:25,500 --> 00:04:29,540 The PIM bootstrap router protocol uses the exact same multicast address 60 00:04:29,540 --> 00:04:34,540 as normal PIM uses, 2240013. 61 00:04:34,540 --> 00:04:38,400 And there are some situations when using this feature that unicast messages 62 00:04:38,400 --> 00:04:40,500 go out as well. And I'll talk about that.