组播路由协议详细图解

1、PIM Sparse Mode Details© 2002, Cisco Systems, Inc.s.PIM Sparse Mv1.1-1ObjectivesUpon completion of this section you will beable to: Describe the control messages in PIM SM and their significance in building distribution trees Read the multicast forwarding table and identify the flags and timers

2、 associated with various multicast states Explain the maintenance of a PIM SM distribution treePIM Neighbor DiscoveryDesignated Router (DR):Highest DR-Priority or Highest IP Address171.68.37.2PIM Router 2PIM HelloPIM HelloPIM Router 1171.68 37.1PIMv2 Hellos are periodically multicast to the “All-PIM

3、-Routers” (224.0.0.13) group address.(Default = 30 seconds)Note: PIMv1 multicasts PIM Query messages to the “All-Routers” (224.0.0.2) group address.If the DR times-out, a new DR is elected.The DR is responsible for sending all Join and Register messages for any receivers orsenders on the network.PIM

4、 Neighbor Discovery (cont.)R2#show ip pim neighbor PIM Neighbor TableMode: B - Bidir Capable, DR - Designated Router, N - DefauR Priority,S - State Refresh CapableNeighborInterfaceUptime/ExpiresVerDR AddressPrio/Mode1.1.1.3FastEthernet0/000:01:40/00:01:33 v21 / DR S1.1.1.1FastEthernet0/000:01:40/00:

5、01:33 v21 / S27.1.1.7Serial3/000:00:27/00:01:17 v21 / SR2#show ip pim interfaceAddress InterfaceVer/ Nbr Query DR DRMode Count Intvl Prior1.1.1.2 FastEthernet0/0 v2/S 2 30 1 1.1.1.3 27.1.1.2 Serial3/0v2/S 1 30 1 0.0.0.0 23.1.1.2 Serial3/1v2/S 0 30 1 0.0.0.0PIM State组播路由条目：描述在组播分发树中路由器的组播分发状态Represen

6、ted by entries in the multicast routing (mroute) tableUsed to make multicast traffic forwarding decisionsComposed of (*, G) and (S, G) entriesEach entry contains RPF information Incoming (i.e. RPF) interface RPF Neighbor (upstream)Each entry contains an Outgoing Interface List (OIL) OIL may be NULLP

7、IM SM State Examplesj-mbone> show ip mroute IP Multicast Routing TableFlags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected L - Local, P - Pruned, R - RP-bit set, F - Register flag,T - SPT-bit set, J - Join SPT, M - MSDP created entry,X - Proxy Join Timer Running, A - Advert

8、ised via MSDP, U - URD,I - Received Source Specific Host Report Outgoing interface flags: H - Hardware switched Timers: Uptime/ExpiresInterface state: Interface, Next-Hop or VCD, State/Mode(*, 224.1.2.3), 00:07:54/00:02:59, RP 10.127.0.7, flags: SIncoming interface: Null, RPF nbr 0.0.0.0 Outgoing in

9、terface list:Serial1/3, Forward/Sparse, 00:07:54/00:02:32(10.139.17.126, 224.1.2.3), 00:01:29/00:02:08, flags: TAIncoming interface: Serial1/4, RPF nbr 10.139.16.130Outgoing interface list:Serial1/3, Forward/Sparse, 00:00:57/00:02:02PIM SM (*, G) State Rules(*, G) creation Receipt of a PIM (*, G) Jo

10、in or IGMP report Automatically if (S, G) must be created(*, G) reflects default group forwarding IIF = RPF interface toward RP OIL = interfacesthat received a (*, G) Join orwith directly connected members or manually configured(*, G) deletion When OIL = NULL and No child (S, G) state exists（子项消失后3分

11、钟消失）PIM SM (S, G) State Rules (cont.)(S, G) creationBy receipt of (S, G) JoinBy receipt of traffic from a directly connected source By Register processParent (*, G) created (if does not exist)(S, G) reflects forwarding of “S” to “G” IIF = RPF Interface normally toward source RPF toward RP if “RP-bit

12、” set OIL = Initially, copy of (*, G) OIL minus IIF(S, G) deletion By normal (S, G) entry timeoutPIM SM OIL RulesInterfaces in OIL addedFor (*,G)-By receipt of PIM (*,G) Join or IGMP report message For (S,G)-By receipt of PIM (S,G) join or IGMP report message注意: (S,G)和(*,G)的出接口没有必然器的出接口上才必然保持一致Inter

13、faces in OIL removed,只有在最后一跳路由 By receipt of Prune message or IGMP leave message Interface Expire timer counts down to zero Timer reset (to 3 minutes) by receipt of periodic Joinor By IGMP Membership ReportPIM SM State FlagsS = Sparse ModeC = Directly Connected Host L = Local (Router is member)P = P

14、runed (All intfcs in OIL = Prune) T = Forwarding via SPT Indicates at least one packet was forwardedPIM SM State Flags (cont.)J = Join SPT In (*, G) entry Indicates SPT-Threshold is being exceeded Next (S, G) received will trigger join of SPT In (S, G) entry Indicates SPT joined because of SPT-Thres

15、hold If rate < SPT-Threshold, switch back to shared treeF = Register In (S, G) entry “S” is a directly connected source Triggers the Register Process In (*, G) entry Set when “F” set in at least one child (S, G)PIM SM ForwardingSource Tree (SPT)Multicast Packetsto RP(10.1.5.1)S1Shared TreeMultica

16、st PacketsS0(128.9.160.43,224.1.1.1)rtr-a(128.9.160.1, 224.1.1.1)E0E0E1Rcvr A (*, 224.1.1.1) Packets are forwarded out all interfaces in OIL PIM Sparse mode interfaces are placed on the “oilist” for a Multicast Group if:PIM neighbor joins the group on this interfaceHost on this interface has joined

17、the groupInterface has been manually configured to join groupPIM SM JoiningLeaf routers send a (*, G) Join toward RP Joins sent hop-by-hop along path toward RPEach router along path creates (*, G) state IF no (*, G) state, Create it and send a Join toward RP. ELSE Join process complete. Reached the

18、shared tree.PIM SM JoiningS1To RP (10.1.5.1)rtr-aS010.1.4.2E010 1.2.110.1.2.2E0E1rtr-b1IGMP JoinRcvr Artr-b creates (*, 224.1.1.1) stateRcvr A wants to receive group G traffic. Sends IGMP Join for G.1(*, 224.1.1.1), 00:00:05/00:02:54, RP 10.1.5.1, flags: SCIncoming interface: Ethernet0, RPF nbr 10.1

19、.2.1Outgoing interface list:Ethernet1, Forward/Sparse, 00:00:05/00:02:54Shared TreePIM SM JoiningS1To RP (10.1.5.1)rtr-aS010.1.4.2E010 1.2.110.1.2.22PIM JoinE0E1rtr-bRcvr Artr-a creates (*, 224.1.1.1) state.Rcvr A wants to receive group G traffic. Sends IGMP Join for G.rtr-b sends (*, G) Join toward

20、 RP.12(*, 224.1.1.1), 00:00:05/00:02:54, RP 10.1.5.1, flags: SIncoming interface: Serial0, RPF nbr 10.1.4.1Outgoing interface list:Ethernet0, Forward/Sparse, 00:00:05/00:02:54Shared TreePIM SM Joining4Shared TreeS1To RP (10.1.5.1)rtr-aS010.1.4.23PIM JoinE010 1.2.110.1.2.2E0E1rtr-bRcvr A1Rcvr A wants

21、 to receive group G traffic.rtr-b sends (*, G) Join toward RP.Sends IGMP Join for G.23rtr-a sends (*, G) Join toward RP.Shared tree is built all the way back to the RP.4Shared TreePIM SM RegisteringSenders begin sending multicast traffic Senders dont necessarily perform IGMP group joinsFirst-hop rou

22、ter unicasts Registers to RP A multicast packet is encapsulated in each Register message Registers messages follow unicast path to RPRP receives “Register” messagesDe-encapsulates Mcast packet inside Register msgForwards Mcast packet down Shared TreeSends (S, G) Join toward Source/first-hop router t

23、o build an (S, G)SPT between Source and RPPIM SM Registering (cont.)First-hop router receives (S, G) JoinSPT between Source and RP now builtBegins forwarding traffic down SPT to RP(S, G) Traffic temporarily flowing down 2 paths to RPRP receives multicast traffic from SPT Sends a Register-Stop msg to

24、 Source/first-hop routerFirst-hop router receives Register-Stop Stops encapsulating traffic in Register messages Multicast Traffic now flowing down single SPT to RPPIM SM RegisteringReceiver Joins FirstRPS3E0S0S0S1S0S1rtr-crtr-artr-bShared TreeState in RP before any source registers (receivers on sh

25、ared tree); empty states forgroup 224.1.1.1 in rtr-a and rtr-b(*, 224.1.1.1), 00:00:03/00:02:56, RP 171.68.28.140, flags:SIncoming interface: Null, RPF nbr 0.0.0.0,Outgoing interface list:Serial0, Forward/Sparse, 00:03:14/00:02:59Serial1, Forward/Sparse, 00:03:14/00:02:59PIM SM RegisteringReceiver J

26、oins First(171.68.37.121, 224.1.1.1)Mcast Packets2Register MsgsRP1SourceS3E0S0S0S1171.68.37.121S0S1rtr-crtr-artr-bShared Treertr-a creates (S, G) state for source(After automatically creating a (*, G) entry)Source begins sending group G traffic.rtr-a encapsulates packets in Registers; unicasts to RP

27、.12(*, 224.1.1.1), 00:00:03/00:02:56, RP 171.68.28.140, flags: SPIncoming interface: Serial0, RPF nbr 171.68.28.191,Outgoing interface list: Null(171.68.37.121/32, 224.1.1.1), 00:00:03/00:02:56, flags: FPTIncoming interface: Ethernet0, RPF nbr 0.0.0.0, RegisteringOutgoing interface list: NullPIM SM

28、RegisteringReceiver Joins First(171.68.37.121, 224.1.1.1)Mcast PacketsRegister Msgs171.68.28.139RPSourceS3E0S0S0S1171.68.37.121S0S1rtr-c3rtr-artr b(*, 224.1.1.1)Mcast TrafficShared TreeRP processes Register; creates (S, G) statertr-c (RP) de-encapsulates packets; forwards down shared tree.3(*, 224.1

29、.1.1), 00:09:21/00:02:38, RP 171.68.28.140, flags: SIncoming interface: Null, RPF nbr 0.0.0.0,Outgoing interface list:Serial0, Forward/Sparse, 00:09:21/00:02:38Serial1, Forward/Sparse, 00:03:14/00:02:46(171.68.37.121, 224.1.1.1, 00:01:15/00:02:46, flags:Incoming interface: Serial3, RPF nbr 171.68.28

30、.139, Outgoing interface list:Serial0, Forward/Sparse, 00:00:49/00:02:11 Serial1, Forward/Sparse, 00:00:49/00:02:11PIM SM RegisteringReceiver Joins First(171.68.37.121, 224.1.1.1)Mcast PacketsRegister MsgsRPSourceE0S0S0S1171.68.37.121S0S1rtr-crtr-artr-b(*, 224.1.1.1)Mcast Traffic171.68.28.190Shared

31、Treertr-b processes Join, creates (S, G) state(After automatically creating the (*, G) entry)RP sends (S, G) Join toward Source to build SPT.rtr-b sends (S, G) Join toward Source to continue building SPT.45(*, 224.1.1.1), 00:04:28/00:01:32, RP 171.68.28.140, flags: SPIncoming interface: Serial1, RPF

32、 nbr 171.68.28.140,Outgoing interface list: Null(171.68.37.121/32, 224.1.1.1), 00:04:28/00:01:32, flags:Incoming interface: Serial0, RPF nbr 171.68.28.190Outgoing interface list:Serial1, Forward/Sparse, 00:04:28/00:01:32Join5Join4PIM SM RegisteringReceiver Joins First(171.68.37.121, 224.1.1.1)Mcast

33、PacketsRegister MsgsRPSourceE0S0S0S1171.68.37.121S0S1rtr-crtr-artr-b(*, 224.1.1.1)Mcast TrafficShared Treertr-a processes the (S, G) Join; adds Serial0 to OIL(*, 224.1.1.1), 00:04:28/00:01:32, RP 171.68.28.140, flags: SPIncoming interface: Serial0, RPF nbr 171.68.28.191,Outgoing interface list: Null

34、(171.68.37.121/32, 224.1.1.1), 00:04:28/00:01:32, flags: FTIncoming interface: Ethernet0, RPF nbr 0.0.0.0, RegisteringOutgoing interface list:Serial0, Forward/Sparse, 00:04:28/00:01:32PIM SM RegisteringReceiver Joins First(171.68.37.121, 224.1.1.1)Mcast PacketsRegister MsgsRPSourceE0S0S0S1171.68.37.

35、121S1rtr-cS0rtr-artr-b(*, 224.1.1.1)Mcast TrafficRegister-Stop7Shared Tree6RP begins receiving (S, G) traffic down SPT.RP sends Register-Stop to rtr-a.76PIM SM RegisteringReceiver Joins First(171.68.37.121, 224.1.1.1)Mcast Packets8RPSourceS3E0S0S0S1171.68.37.121S0S1rtr-crtr-artr-b(*, 224.1.1.1)Mcast

36、 TrafficShared Treertr-a stops sending Register messages(Final State in rtr-a)(S, G) Traffic now flowing down a single path (SPT) to RP.8(*, 224.1.1.1), 00:04:28/00:01:32, RP 171.68.28.140, flags: SPIncoming interface: Serial0, RPF nbr 171.68.28.191,Outgoing interface list: Null(171.68.37.121/32, 22

37、4.1.1.1), 00:04:28/00:01:32, flags: FTIncoming interface: Ethernet0, RPF nbr 0.0.0.0, Outgoing interface list:Serial0, Forward/Sparse, 00:04:28/00:01:32PIM SM RegisteringSource Starts FirstRPE0S0S0S1S3S0S1rtr-crtr-artr-bEmpty state in RP before any source registers (no receivers on shared tree); emp

38、tystates for group 224.1.1.1 in rtr-a and rtr-b also.rtr-c>show ip mroute 224.1.1.1Group 224.1.1.1 not found.PIM SM RegisteringSource Starts First2(171.68.37.121, 224.1.1.1)Mcast PacketsRegister MsgsRP1SourceE0S0S0S1S3171.68.37.121S0S1rtr-crtr-artr-brtr-a creates (S, G) state for source(After aut

39、omatically creating a (*, G) entry)Source begins sending Group G traffic.rtr-a encapsulates packets in Registers; unicasts to RP.12(*, 224.1.1.1), 00:00:03/00:02:56, RP 171.68.28.140, flags: SPIncoming interface: Serial0, RPF nbr 171.68.28.191,Outgoing interface list: Null(171.68.37.121/32, 224.1.1.

40、1), 00:00:03/00:02:56, flags: FPTIncoming interface: Ethernet0, RPF nbr 0.0.0.0,Outgoing interface list: NullPIM SM RegisteringSource Starts First(171.68.37.121, 224.1.1.1)Mcast PacketsRegister Msgs171.68.28.139RP3rtr-cSourceE0S0S0S1S3171.68.37.121S0S1rtr-artr-bRP processes Register; creates (S, G)

41、state(After automatically creating the (*, G) entry)rtr-c (RP) has no receivers on shared tree; discards packet.3(*, 224.1.1.1), 00:01:15/00:01:45, RP 171.68.28.140, flags: SIncoming interface: Null, RPF nbr 0.0.0.0,Outgoing interface list: Null(171.68.37.121, 224.1.1.1), 00:01:15/00:01:45, flags: P

42、Incoming interface: Serial3, RPF nbr 171.68.28.139,Outgoing interface list: NullPIM SM RegisteringSource Starts First(171.68.37.121, 224.1.1.1)Mcast PacketsRegister MsgsRPSourceE0S0S0S1S3171.68.37.121S0S1rtr-crtr-artr-b54Register-Stop345rtr-c (RP) has no receivers on shared tree; discards packet.RP

43、sends Register-Stop to rtr-a.rtr-a stops encapsulating traffic in Register Messages;drops packets from Source.PIM SM RegisteringSource Starts First(171.68.37.121, 224.1.1.1)Mcast PacketsRPSourceE0S0S0S1S3171.68.37.121S0S1rtr-crtr-artr-bState in rtr-a after Registering(without receivers on shared tre

44、e)(*, 224.1.1.1), 00:01:28/00:01:32, RP 171.68.28.140, flags: SPIncoming interface: Serial0, RPF nbr 171.68.28.191,Outgoing interface list: Null(171.68.37.121/32, 224.1.1.1), 00:01:28/00:01:32, flags: FPTIncoming interface: Ethernet0, RPF nbr 0.0.0.0Outgoing interface list: NullPIM SM RegisteringSou

45、rce Starts First(171.68.37.121, 224.1.1.1)Receivers begin joining the Shared TreeMcast Packets7JoinRPSourceE0S0S0S1S3171.68.37.121S0S1rtr-crtr-artr-b6(*, G) JoinRP processes (*, G) Join(Adds Serial1 to Outgoing Interface Lists)RP (rtr-c) receives (*, G) Join from a receiver on shared tree.RP sends (

46、S, G) Joins for all known Sources in Group.67(*, 224.1.1.1), 00:09:21/00:02:38, RP 171.68.28.140, flags: SIncoming interface: Null, RPF nbr 0.0.0.0, Outgoing interface list:Serial1, Forward/Sparse, 00:00:14/00:02:46(171.68.37.121/32, 224.1.1.1, 00:01:15/00:02:46, flags: TIncoming interface: Serial3,

47、 RPF nbr 171.68.28.139,Outgoing interface list:Serial1, Forward/Sparse, 00:00:14/00:02:46PIM SM RegisteringSource Starts First(171.68.37.121, 224.1.1.1)Mcast Packets78JoinJoinRPSourceE0S0S0S1S3171.68.37.121S0S1rtr-crtr-artr-b171.68.28.190rtr-b processes Join, creates (S, G) state(After automatically

48、 creating the (*, G) entry)RP sends (S, G) Joins for all known Sources in Group.rtr-b sends (S, G) Join toward Source to continue building SPT.78(*, 224.1.1.1), 00:04:28/00:01:32, RP 171.68.28.140, flags: SPIncoming interface: Serial1, RPF nbr 171.68.28.140,Outgoing interface list: Null(171.68.37.12

49、1/32, 224.1.1.1), 00:04:28/00:01:32, flags:Incoming interface: Serial0, RPF nbr 171.68.28.190Outgoing interface list:Serial1, Forward/Sparse, 00:04:28/00:01:32PIM SM RegisteringSource Starts First(171.68.37.121, 224.1.1.1)Mcast Packets9RPSourceE0S0S0S1S3171.68.37.121S0S1rtr-c10rtr-artr-b(*, 224.1.1.

50、1)Mcast Trafficrtr-a processes the (S, G) Join; adds Serial0 to OILRP begins receiving (S, G) traffic down SPT.RP forwards (S, G) traffic down shared tree to receivers.910(*, 224.1.1.1), 00:04:28/00:01:32, RP 171.68.28.140, flags: SPIncoming interface: Serial0, RPF nbr 171.68.28.191,Outgoing interfa

51、ce list: Null(171.68.37.121/32, 224.1.1.1), 00:04:28/00:01:32, flags: FTIncoming interface: Ethernet0, RPF nbr 0.0.0.0, RegisteringOutgoing interface list:Serial0, Forward/Sparse, 00:04:28/00:01:32PIM SM RegisteringReceivers Along the SPT(171.68.37.121, 224.1.1.1)Mcast PacketsRPSourceS0rtr-bS1S3171.68.37.121rtr-cS1rtr-a(*, 224.1.1.1)Mcast TrafficCurrent state in rtr-b(*, 224.1.1.1), 00:04:28/00:01:32, RP 171.68.28.140, flags: SPIncoming interface: Serial1, RPF nbr 171.68.28.140,Outgoing interface list: Null(171.68.37.121/32, 224.1.1.1), 00:04