IP多播技術介紹（三）

實例2：在幀中繼的網絡環境

拓撲圖以下所示：

具體配置以下

R1#sh running-config Building configuration... Current configuration : 1718 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R1 ! boot-start-marker boot-end-marker ! ! no aaa new-model ! resource policy ! ip subnet-zero ip cef ! ! ! ! ip multicast-routing ! ! ! ! ! ! ! ! interface FastEthernet0/0 ip address 10.1.1.1 255.255.255.0 ip pim dense-mode duplex half ! interface Serial1/0 no ip address encapsulation frame-relay serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/0.305 point-to-point ip address 10.2.1.1 255.255.255.0 ip pim dense-mode frame-relay interface-dlci 305 ! interface Serial1/0.309 point-to-point ip address 10.2.2.1 255.255.255.0 ip pim dense-mode frame-relay interface-dlci 309 ! interface Serial1/1 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/2 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/3 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Ethernet2/0 no ip address shutdown duplex half ! interface Ethernet2/1 no ip address shutdown duplex half ! interface Ethernet2/2 no ip address shutdown duplex half ! interface Ethernet2/3 no ip address shutdown duplex half ! router ospf 10 log-adjacency-changes network 10.1.1.0 0.0.0.255 area 0 network 10.2.1.0 0.0.0.255 area 0 network 10.2.2.0 0.0.0.255 area 0 ! ip classless no ip http server no ip http secure-server ! ! ! logging alarm informational ! ! ! ! control-plane ! ! ! ! ! ! gatekeeper shutdown ! ! line con 0 exec-timeout 0 0 stopbits 1 line aux 0 stopbits 1 line vty 0 4 ! ! End ——————————————————————————————————————— R2#sh running-config Building configuration... Current configuration : 1819 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R2 ! boot-start-marker boot-end-marker ! ! no aaa new-model ! resource policy ! ip subnet-zero ip cef ! ! ! ! ip multicast-routing ! ! ! ! ! ! interface FastEthernet0/0 no ip address shutdown duplex half ! interface Serial1/0 no ip address encapsulation frame-relay serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/0.503 point-to-point ip address 10.2.1.2 255.255.255.0 ip pim dense-mode frame-relay interface-dlci 503 ! interface Serial1/0.506 point-to-point ip address 10.2.4.2 255.255.255.0 ip pim dense-mode frame-relay interface-dlci 506 ! interface Serial1/0.507 point-to-point ip address 10.2.5.2 255.255.255.0 ip pim dense-mode frame-relay interface-dlci 507 ! interface Serial1/1 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/2 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/3 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Ethernet2/0 no ip address shutdown duplex half ! interface Ethernet2/1 no ip address shutdown duplex half ! interface Ethernet2/2 no ip address shutdown duplex half ! interface Ethernet2/3 no ip address shutdown duplex half ! router ospf 10 log-adjacency-changes network 10.2.1.0 0.0.0.255 area 0 network 10.2.4.0 0.0.0.255 area 0 network 10.2.5.0 0.0.0.255 area 0 ! ip classless no ip http server no ip http secure-server ! ! ! logging alarm informational ! ! ! ! control-plane ! ! ! ! ! ! gatekeeper shutdown ! ! line con 0 exec-timeout 0 0 stopbits 1 line aux 0 stopbits 1 line vty 0 4 ! ! End ——————————————————————————————————————— R3#sh running-config Building configuration... Current configuration : 1654 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R3 ! boot-start-marker boot-end-marker ! ! no aaa new-model ! resource policy ! ip subnet-zero ip cef ! ! ! ! ip multicast-routing ! ! ! ! ! ! ! interface FastEthernet0/0 no ip address shutdown duplex half ! interface Serial1/0 no ip address encapsulation frame-relay serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/0.903 point-to-point ip address 10.2.2.2 255.255.255.0 ip pim dense-mode frame-relay interface-dlci 903 ! interface Serial1/0.906 point-to-point ip address 10.2.3.1 255.255.255.0 ip pim dense-mode frame-relay interface-dlci 906 ! interface Serial1/1 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/2 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/3 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Ethernet2/0 no ip address shutdown duplex half ! interface Ethernet2/1 no ip address shutdown duplex half ! interface Ethernet2/2 no ip address shutdown duplex half ! interface Ethernet2/3 no ip address shutdown duplex half ! router ospf 10 log-adjacency-changes network 10.2.2.0 0.0.0.255 area 0 network 10.2.3.0 0.0.0.255 area 0 ! ip classless no ip http server no ip http secure-server ! ! ! logging alarm informational ! ! ! ! control-plane ! ! ! ! ! ! gatekeeper shutdown ! ! line con 0 exec-timeout 0 0 stopbits 1 line aux 0 stopbits 1 line vty 0 4 ! ! end ——————————————————————————————————————— R4#sh running-config Building configuration... Current configuration : 1718 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R4 ! boot-start-marker boot-end-marker ! ! no aaa new-model ! resource policy ! ip subnet-zero ip cef ! ! ! ! ip multicast-routing ! ! ! ! ! interface FastEthernet0/0 ip address 10.1.2.1 255.255.255.0 ip pim dense-mode duplex full ! interface Serial1/0 no ip address encapsulation frame-relay serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/0.605 point-to-point ip address 10.2.4.1 255.255.255.0 ip pim dense-mode frame-relay interface-dlci 605 ! interface Serial1/0.609 point-to-point ip address 10.2.3.2 255.255.255.0 ip pim dense-mode frame-relay interface-dlci 609 ! interface Serial1/1 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/2 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/3 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Ethernet2/0 no ip address shutdown duplex half ! interface Ethernet2/1 no ip address shutdown duplex half ! interface Ethernet2/2 no ip address shutdown duplex half ! interface Ethernet2/3 no ip address shutdown duplex half ! router ospf 10 log-adjacency-changes network 10.1.2.0 0.0.0.255 area 0 network 10.2.3.0 0.0.0.255 area 0 network 10.2.4.0 0.0.0.255 area 0 ! ip classless no ip http server no ip http secure-server ! ! ! logging alarm informational ! ! ! ! control-plane ! ! ! ! ! ! gatekeeper shutdown ! ! line con 0 exec-timeout 0 0 stopbits 1 line aux 0 stopbits 1 line vty 0 4 ! ! end ——————————————————————————————————————— R5#sh running-config Building configuration... Current configuration : 1554 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R5 ! boot-start-marker boot-end-marker ! ! no aaa new-model ! resource policy ! ip subnet-zero ip cef ! ! ! ! ip multicast-routing ! ! ! ! interface FastEthernet0/0 ip address 10.1.2.25 255.255.255.0 ip pim dense-mode duplex full ! interface Serial1/0 no ip address encapsulation frame-relay serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/0.705 point-to-point ip address 10.2.5.1 255.255.255.0 ip pim dense-mode frame-relay interface-dlci 705 ! interface Serial1/1 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/2 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/3 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Ethernet2/0 no ip address shutdown duplex half ! interface Ethernet2/1 no ip address shutdown duplex half ! interface Ethernet2/2 no ip address shutdown duplex half ! interface Ethernet2/3 no ip address shutdown duplex half ! router ospf 10 log-adjacency-changes network 10.1.2.0 0.0.0.255 area 0 network 10.2.5.0 0.0.0.255 area 0 ! ip classless no ip http server no ip http secure-server ! ! ! logging alarm informational ! ! ! ! control-plane ! ! ! ! ! ! gatekeeper shutdown ! ! line con 0 exec-timeout 0 0 stopbits 1 line aux 0 stopbits 1 line vty 0 4 ! ! end

配置完成後，一樣打開組播測試工具，一個發送源，一個爲接收成員。

Show ip mroute 查看組播路由表項。

R1#sh ip mroute IP Multicast Routing Table Flags: 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 - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group Outgoing interface flags: H - Hardware switched, A - Assert winner Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 224.0.1.40), 00:58:14/00:02:27, RP 0.0.0.0, flags: DCL Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.309, Forward/Dense, 00:57:11/00:00:00 Serial1/0.305, Forward/Dense, 00:57:12/00:00:00 FastEthernet0/0, Forward/Dense, 00:58:14/00:00:00 (*, 228.13.20.216), 00:41:26/stopped, RP 0.0.0.0, flags: DC Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: FastEthernet0/0, Forward/Dense, 00:16:33/00:00:00 Serial1/0.309, Forward/Dense, 00:41:26/00:00:00 Serial1/0.305, Forward/Dense, 00:41:26/00:00:00 (10.1.1.88, 228.13.20.216), 00:13:37/00:02:52, flags: T Incoming interface: FastEthernet0/0, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.305, Forward/Dense, 00:13:24/00:00:00 Serial1/0.309, Prune/Dense, 00:02:13/00:00:47 (*, 239.255.255.250), 00:57:33/00:02:27, RP 0.0.0.0, flags: DC Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.309, Forward/Dense, 00:57:12/00:00:00 Serial1/0.305, Forward/Dense, 00:57:13/00:00:00 FastEthernet0/0, Forward/Dense, 00:57:33/00:00:00

從上面狀態能夠看到，(10.1.1.88, 228.13.20.216)處於T（表示路由器是SPT中和一個有效成員）狀態，在入站接口的RPF的nbr爲0.0.0.0則說明所鏈接的設備爲多播組的源。

在路由器R1上查看單播路由表，

R1#sh ip route Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route Gateway of last resort is not set 10.0.0.0/24 is subnetted, 7 subnets C 10.2.1.0 is directly connected, Serial1/0.305 O 10.1.2.0 [110/129] via 10.2.2.2, 00:50:00, Serial1/0.309 [110/129] via 10.2.1.2, 00:50:00, Serial1/0.305 C 10.2.2.0 is directly connected, Serial1/0.309 C 10.1.1.0 is directly connected, FastEthernet0/0 O 10.2.3.0 [110/128] via 10.2.2.2, 00:50:00, Serial1/0.309 O 10.2.4.0 [110/128] via 10.2.1.2, 00:50:00, Serial1/0.305 O 10.2.5.0 [110/128] via 10.2.1.2, 00:50:00, Serial1/0.305

去往10.1.2.0的路由有兩條，其路徑開銷是相同的，這須要選擇IP地址小的爲最優路徑。

R2#sh ip mroute IP Multicast Routing Table Flags: 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 - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group Outgoing interface flags: H - Hardware switched, A - Assert winner Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 224.0.1.40), 00:45:02/stopped, RP 0.0.0.0, flags: DCL Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.507, Forward/Dense, 00:43:47/00:00:00 Serial1/0.506, Forward/Dense, 00:43:50/00:00:00 Serial1/0.503, Forward/Dense, 00:44:01/00:00:00 (*, 228.13.20.216), 00:28:15/stopped, RP 0.0.0.0, flags: D Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.507, Forward/Dense, 00:28:15/00:00:00 Serial1/0.506, Forward/Dense, 00:28:15/00:00:00 Serial1/0.503, Forward/Dense, 00:28:15/00:00:00 (10.1.1.88, 228.13.20.216), 00:00:13/00:02:59, flags: T Incoming interface: Serial1/0.503, RPF nbr 10.2.1.1 Outgoing interface list: Serial1/0.506, Forward/Dense, 00:00:13/00:00:00 Serial1/0.507, Forward/Dense, 00:00:13/00:00:00

R3#sh ip mroute IP Multicast Routing Table Flags: 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 - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group Outgoing interface flags: H - Hardware switched, A - Assert winner Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 224.0.1.40), 00:49:49/stopped, RP 0.0.0.0, flags: DCL Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.906, Forward/Dense, 00:48:48/00:00:00 Serial1/0.903, Forward/Dense, 00:48:48/00:00:00 (*, 228.13.20.216), 00:32:46/stopped, RP 0.0.0.0, flags: D Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.906, Forward/Dense, 00:32:46/00:00:00 Serial1/0.903, Forward/Dense, 00:32:46/00:00:00 (10.1.1.88, 228.13.20.216), 00:02:36/00:00:23, flags: PT Incoming interface: Serial1/0.903, RPF nbr 10.2.2.1 Outgoing interface list: Serial1/0.906, Prune/Dense, 00:02:35/00:00:23, A

R4#sh ip mroute IP Multicast Routing Table Flags: 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 - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group Outgoing interface flags: H - Hardware switched, A - Assert winner Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 224.0.1.40), 00:48:55/00:02:47, RP 0.0.0.0, flags: DCL Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.605, Forward/Dense, 00:47:52/00:00:00 Serial1/0.609, Forward/Dense, 00:47:52/00:00:00 FastEthernet0/0, Forward/Dense, 00:48:55/00:00:00 (*, 228.13.20.216), 00:32:17/stopped, RP 0.0.0.0, flags: DC Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.609, Forward/Dense, 00:32:17/00:00:00 Serial1/0.605, Forward/Dense, 00:32:17/00:00:00 FastEthernet0/0, Forward/Dense, 00:32:17/00:00:00 (10.1.1.88, 228.13.20.216), 00:26:11/00:01:37, flags: PT Incoming interface: Serial1/0.605, RPF nbr 10.2.4.2 Outgoing interface list: FastEthernet0/0, Prune/Dense, 00:01:13/00:01:46 Serial1/0.609, Prune/Dense, 00:23:08/00:00:56, A (*, 239.255.255.250), 00:04:16/00:02:47, RP 0.0.0.0, flags: DC Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.609, Forward/Dense, 00:04:16/00:00:00 Serial1/0.605, Forward/Dense, 00:04:16/00:00:00 FastEthernet0/0, Forward/Dense, 00:04:16/00:00:00

R5#sh ip mroute IP Multicast Routing Table Flags: 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 - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group Outgoing interface flags: H - Hardware switched, A - Assert winner Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 224.0.1.40), 00:47:01/00:02:39, RP 0.0.0.0, flags: DCL Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.705, Forward/Dense, 00:45:59/00:00:00 FastEthernet0/0, Forward/Dense, 00:47:01/00:00:00 (*, 228.13.20.216), 00:30:27/stopped, RP 0.0.0.0, flags: DC Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.705, Forward/Dense, 00:30:27/00:00:00 FastEthernet0/0, Forward/Dense, 00:30:27/00:00:00 (10.1.1.88, 228.13.20.216), 00:02:38/00:02:50, flags: T Incoming interface: Serial1/0.705, RPF nbr 10.2.5.2 Outgoing interface list: FastEthernet0/0, Forward/Dense, 00:02:25/00:00:00, A (*, 239.255.255.250), 00:02:25/00:02:34, RP 0.0.0.0, flags: DC Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.705, Forward/Dense, 00:02:27/00:00:00 FastEthernet0/0, Forward/Dense, 00:02:27/00:00:00 R4#sh ip pim neighbor PIM Neighbor Table Neighbor Interface Uptime/Expires Ver DR Address Prio/Mode 10.1.2.25 FastEthernet0/0 00:59:55/00:01:23 v2 1 / DR S 10.2.4.2 Serial1/0.605 00:59:22/00:01:24 v2 1 / S 10.2.3.1 Serial1/0.609 00:59:22/00:01:30 v2 1 / S

根據規則選擇出DR。

六、PIM-SM（Protocol Independent Multicast Sparse Mode）

PIM-SM使用了7種PIMV2消息：

l Hello

l Bootstrap（引導）

l Candidate-RP-Advertisement（候選RP宣告）

l Join/Prune（加入/剪除）

l Assert（聲明）

l Register（註冊）

l Register-Stop（註冊終止）

Hello、Join/Prune、Assert這三種消息也在PIM-DM中使用，而另外四種消息上PIM-SM所獨有的。正如PIM-DM中有兩個獨有的消息（Graft與Graft-ack）同樣。

在 PIM-SM 域中，運行 PIM-SM 協議的路由器週期性的發送 Hello 消息，用以發現鄰接的 PIM 路由器，而且負責在多路訪問網絡中進行 DR 的選舉。這裏，DR 負責爲與其直連的組成員向組播樹根節點的方向發送「加入/剪枝」消息，或是將直連組播源的數據發向組播分發樹。

PIM-SM 經過創建組播分發樹來進行組播數據包的轉發。組播分發樹分爲兩種：以組 G 的 RP 爲根的共享樹和以組播源爲根的最短路徑樹。PIM-SM 經過顯式的加入/剪枝機制來完成組播分發樹的創建與維護。

PIM-SM 中還涉及到 RP 的選擇機制。在 PIM-SM 域內配置了一個或多個候選自舉路由器(Candidate-BSR)。使用必定的規則從中選出自舉路由器 (BSR) 。PIM-SM 域中還配置有候選 RP 路由器(Candidate-RP)，這些候選 RP 將包含了它們地址及能夠服務的組播組等信息的報文單播發送給自舉路由器，再由 BSR 按期生成包括一系列候選 RP 以及相應的組地址的「自舉」消息。「自舉」消息在整個域中逐跳發送。路由器接收並保存這些「自舉」消息。若 DR 從直連主機收到了 IGMP 加入報文後，若是它沒有這個組的路由項，將使用 hash 算法將組地址映射到一個候選 RP。而後朝 RP 方向逐跳組播「加入/剪枝」消息。若 DR 從直連主機收到組播數據包，若是它沒有這個組的路由項，也將使用 hash 算法將組地址映射到一個候選 RP，而後將組播數據封裝在註冊消息中單播發送到 RP。

在多路訪問網絡中，PIM-SM 還引入瞭如下機制：使用斷言機制選舉惟一的轉發者，以防向同一網段重複轉發組播數據包；使用加入/剪枝抑制機制減小冗餘的加入/剪枝消息；使用剪枝否決機制否決不該有的剪枝行爲。

共享樹根植於多播網絡中的一臺路由器，PIM-SM稱之爲會聚點（rendezvous point RP）。在共享樹創建以前，加入的路由器必須知道如何找到RP，路由器能夠經過3種方法知道RP地址：

l 靜態配置RP地址

l 使用Bootstrap自舉協議來指定和宣告RP

l 以思科所私有Auto-RP協議來指定和宣告RP

Bootstrap協議

要運行Bootstrap協議，必須在網絡中指派C-BSR(候選引導路由器)和C-RP（候選聚合點），一般狀況下，通常將同一組路由器同時配置爲C-BSR和C-RP，經過IP地址（環回接口）來區分C-BSR和C-RP。

首先要從C-BSR中選出BSR，每個C-BSR都分配有0~255的優先級（默認爲0）和一個BSR IP地址，當路由器配置成C-BSR時，會啓動一個130秒的引地定時器並偵聽Bootstrap消息。

Bootstrap消息的做用是宣告發起路由器的優先級和BSR IP地址，當C-BSR收到Bootstrap消息後，會將本身的優先級與發起路由器的優先級進行對比，若是發起路由器的優先級較高，由接收路由器會重置本身的引導計時器並繼續偵聽。若是接收路由器的優先級較高，則將本身宣稱爲BSR並開始每隔60秒發送一條Bootstrap消息。如二者的優先級相等，則BSR IP地址較高的路由器爲BSR。

當C-BSR的130秒引導計時器到期時，該路由器將認定網絡中無BSR，則將本身宣稱爲BSR，並開始每隔60秒發送Bootstrap消息。

Bootstrap消息使用所有PIM路由器地址224.0.0.13,且TTL設爲1。當PIM路由器接收到一條Bootstarp消息後，會經過全部接口（接收到該消息的接口除外）向外發送該消息的複本。該處理過程不只能夠將保證Bootstrap消息泛洪到整個多播源，還可保證每臺PIM路由器都能接收到一份消息複本並知道哪臺路由器是BSR。

每臺C-RP都會分配一個RP IP地址和一個0~255之間的優先級，能夠將路由器配置爲某些特定多播組的C-RP，也可配置爲全部多播組的C-RP，當經過接收到的Bootstrap消息知道了BSR以後，C-RP就開始向BSR單播發送Candidate-RP-Advertisement（候選RP宣告）消息，這些消息中包含了發起路由器的RP地址、組地址（發起路由器是該組的候選RP）及其優先級。

BSR將全部有C-RP的優先級及相關的多播組都編譯成RP-set，並經過Bootstrap消息在整個PIM域中宣告該RP-set。此外，Bootstrap消息中還包括一個8bit的hash掩碼。全部路由器都會收到此消息。

當某臺路由器接收到IGMP消息或PIM join消息而要加入某共享樹時，須要檢查接收自BSR的RP-set。

l 若是該多播組只有一個C-RP，由該路由器被選爲RP

l 若是該多播組擁有多個C-RP，且優先級不一樣，則優先級最低的路由器將成爲RP

l 若是該多播組擁有多個C-RP，且優先級相同，則須要運行hash函數。函數輸出值最大的C-RP將成爲RP。

l 若是多個C-RP的hash函數輸出值相同，則IP地址最大的C-RP將成爲RP。

Auto-RP協議

此協議是思科專有的協議，Auto-RP協議與Bootstrap協議相似，須要在PIM-SM環境中指派C-RP，並經過指派的IP地址（環回地址）來標識C-RP，還須要指定一個或多個RP映射代理，其做用與BSR類似。RP映射代理是直接指派的，RP映射代理是將多播映射到RP，而不是宣告RP-set以及在整個多播域中發佈選舉進程。其使用兩個保留地址224.0.1.39和224.0.1.40。當路由器被配置爲一個或多個多播組的C-RP時，它會在RP-Announce（RP通告）消息中宣告本身是這些多播組的C-RP，並每隔60秒將這些消息多播到保留的Cisco-RP-Announce地址224.0.1.39.PIM域中已配置的RP映射代理將偵聽該地址，並從接收到的所有RP-Announce消息中爲該多播組選出一個RP（該多播組的全部C-RP中IP地址最大者將成爲RP）。

映射代理在RP-Discovery（RP發現）消息中宣告完整的group-to-RP映射表，並以60秒爲間隔將這些消息多播到保留的Cisoco-RP-Discovery地址224.0.1.40.全部思科PIM-SM路由器會偵聽該地址，因面能夠掌握每一個多播組的RP狀況。

PIM-SM路由器加入/剪除

在PIM-SM網絡環境中，當PIM-SM DR從某臺主機接收到IGMP成員關係報告消息，想加入到某個多播組時，首先檢查其多播組是否已經存在在該多播組的路由表項，若是存在，那麼接收到該IGMP消息的接口將被加入到路由表項中做爲出站接口。無需再作其它操做。若是多播表中無相應的表項，那就須要爲該多播組建立一個新的（*,G）表項，並加入出站接口。以後該路由器會查找group-to-RP映射列表中的該多播組，查詢單播路由表以找到去往特定RP的路由，並將去住RP的上行接口加入到入站的接口中。以後，該路由器將經過上行出接口向224.0.0.13發出一條join/prune消息，該消息中包含了將要加入的多播組的地址和RP地址，消息中的剪除字段爲空。此外還設置兩個標記（WC-bit和RPT-bit標記）。

當上遊路由器接收到join/prune消息後，會執行下面4種操做中的一種：

l 若是該路由器不是RP路由器，但位於共享樹上，那麼該路由器會將接收到的join/prune消息的接口加入到該多播組的出站接口列表中

l 若是該路由器不是RP路由器，且不位於共享樹上，那麼該路由器將建立一個（*,G）表項。並沿着RP的方向向上遊鄰居發送本身的join/prune消息。

l 若是該路由器是RP，且路由表中已經存在該多播的路由表項，那麼該路由器會將接收到的join/prune消息的接口加入到該多播組的出站接口列表

l 若是該路由器是RP，但其路由表項中沒有該多播的路由表項，那麼該路由器將建立一個（*.G）表項，並將接收到的join/prune消息的接口加入到該多播組的出站接口列表中。

多播樹創建以後，路由器就開始週期性（默認爲60秒）地向上遊發送join/prune消息以保持激活。若是在保持時間（是join/prune消息間隔的3倍，默認爲3分鐘）內PIM路由器沒有從下游鄰居接收到join/prune消息，則將鄰居從其多播組表項的出站接口列表中剪除。

剪除過程與加入過程是同樣的。

源註冊

在共享樹環境中，多播樹的根是核心路由器或聚合點，而不是源，那麼多播源如何將多播分組分發給RP。

當PIM-SM路由器首次接收到其直連多播源的多播分組時，會在其group-to-RP映射表中查找目的多播組的RP。肯定了多播組的RP以後，路由器將多播分組封裝在PIM Register（註冊）消息中，並將該消息發送給RP，須要注意的是，Register消息以單播方式發送到RP地址的。

RP接收到Register消息後，就將多播分組解封裝出來，若是其多播路由表中已存在該多播組的路由表項，則在其出站接口列表中的全部接口上轉發該多播包。

若是須要將大量的多播分組傳送到RP，那麼繼續將多播分組封裝到Register消息中再傳送到RP，效率很是低下，於是RP在其多播表中建立一個（S,G）表項，並經過多播傳送一條join/prune消息來創建一個去住源DR的SPT，這條消息中包含了多播源地址，WC-bit=0且RPT-bit＝0,表示該路徑是有源SPT，而不是共享SPT。

創建了SPT以後，RP就能夠經過該多播樹接收多播流量。此時，路由器須要向多播源的DR發送一條register-stop（消息終止）消息，告訴DR中止在Register消息中發送多播分組。

若是多播源開始向RP發送多播流量的時候沒有組成員，那麼RP將不構建SPT，而是向多播源的DR發送一條Register stop消息，讓其中止在Register 消息中發送被封裝的多播分組。RP有該多播組的（*,G）表項，當有組成員加入時，RP就能夠啓動SPT。

註冊抑制（Register Suppression）機制是用來阻止DR持續不斷的向失效RP發送數據包，當DR接收到Register stop消息後，會啓動註冊抵制定時器（60s）,該路由器會現次經過Register消息發送多播分組。可是在這以前的5s,DR會發送一條攜帶Null-register（空註冊）bit標記的Register消息，若是消息觸發了一條來自RP的Register stop消息，那麼會重置註冊抑制定時器。

實例1：靜態配置RP

實驗拓撲圖以下所示：

具體配置以下：

R1#sh running-config Building configuration... Current configuration : 1757 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R1 ! boot-start-marker boot-end-marker ! ! no aaa new-model ! resource policy ! ip subnet-zero ip cef ! ! ! ! ip multicast-routing ! ! interface FastEthernet0/0 ip address 10.1.1.1 255.255.255.0 ip pim sparse-mode duplex half ! interface Serial1/0 no ip address encapsulation frame-relay serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/0.305 point-to-point ip address 10.2.1.1 255.255.255.0 ip pim sparse-mode frame-relay interface-dlci 305 ! interface Serial1/0.309 point-to-point ip address 10.2.2.1 255.255.255.0 ip pim sparse-mode frame-relay interface-dlci 309 ! interface Serial1/1 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/2 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/3 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Ethernet2/0 no ip address shutdown duplex half ! interface Ethernet2/1 no ip address shutdown duplex half ! interface Ethernet2/2 no ip address shutdown duplex half ! interface Ethernet2/3 no ip address shutdown duplex half ! router ospf 10 log-adjacency-changes network 10.1.1.0 0.0.0.255 area 0 network 10.2.1.0 0.0.0.255 area 0 network 10.2.2.0 0.0.0.255 area 0 ! ip classless no ip http server no ip http secure-server ! ! ip pim rp-address 10.224.1.1 ! logging alarm informational ! ! ! ! control-plane ! ! ! ! ! ! gatekeeper shutdown ! ! line con 0 exec-timeout 0 0 stopbits 1 line aux 0 stopbits 1 line vty 0 4 login ! ! end R1# R2#sh running-config Building configuration... Current configuration : 1858 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R2 ! boot-start-marker boot-end-marker ! ! no aaa new-model ! resource policy ! ip subnet-zero ip cef ! ! ! ! ip multicast-routing ! interface FastEthernet0/0 no ip address shutdown duplex half ! interface Serial1/0 no ip address encapsulation frame-relay serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/0.503 point-to-point ip address 10.2.1.2 255.255.255.0 ip pim sparse-mode frame-relay interface-dlci 503 ! interface Serial1/0.506 point-to-point ip address 10.2.4.2 255.255.255.0 ip pim sparse-mode frame-relay interface-dlci 506 ! interface Serial1/0.507 point-to-point ip address 10.2.5.2 255.255.255.0 ip pim sparse-mode frame-relay interface-dlci 507 ! interface Serial1/1 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/2 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/3 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Ethernet2/0 no ip address shutdown duplex half ! interface Ethernet2/1 no ip address shutdown duplex half ! interface Ethernet2/2 no ip address shutdown duplex half ! interface Ethernet2/3 no ip address shutdown duplex half ! router ospf 10 log-adjacency-changes network 10.2.1.0 0.0.0.255 area 0 network 10.2.4.0 0.0.0.255 area 0 network 10.2.5.0 0.0.0.255 area 0 ! ip classless no ip http server no ip http secure-server ! ! ip pim rp-address 10.224.1.1 ! logging alarm informational ! ! ! ! control-plane ! ! ! ! ! ! gatekeeper shutdown ! ! line con 0 exec-timeout 0 0 stopbits 1 line aux 0 stopbits 1 line vty 0 4 login ! ! end R3#sh running-config Building configuration... Current configuration : 1788 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R3 ! boot-start-marker boot-end-marker ! ! no aaa new-model ! resource policy ! ip subnet-zero ip cef ! ! ! ! ip multicast-routing ! ! ! ! ! interface Loopback0 ip address 10.224.1.1 255.255.255.255 ! interface FastEthernet0/0 no ip address shutdown duplex half ! interface Serial1/0 no ip address encapsulation frame-relay serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/0.903 point-to-point ip address 10.2.2.2 255.255.255.0 ip pim sparse-mode frame-relay interface-dlci 903 ! interface Serial1/0.906 point-to-point ip address 10.2.3.1 255.255.255.0 ip pim sparse-mode frame-relay interface-dlci 906 ! interface Serial1/1 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/2 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/3 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Ethernet2/0 no ip address shutdown duplex half ! interface Ethernet2/1 no ip address shutdown duplex half ! interface Ethernet2/2 no ip address shutdown duplex half ! interface Ethernet2/3 no ip address shutdown duplex half ! router ospf 10 log-adjacency-changes network 10.2.2.0 0.0.0.255 area 0 network 10.2.3.0 0.0.0.255 area 0 network 10.224.1.1 0.0.0.0 area 0 ! ip classless no ip http server no ip http secure-server ! ! ip pim rp-address 10.224.1.1 ! logging alarm informational ! ! ! ! control-plane ! ! ! ! ! ! gatekeeper shutdown ! ! line con 0 exec-timeout 0 0 stopbits 1 line aux 0 stopbits 1 line vty 0 4 login ! ! end R4#sh running-config Building configuration... Current configuration : 1766 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R4 ! boot-start-marker boot-end-marker ! ! no aaa new-model ! resource policy ! ip subnet-zero ip cef ! ! ! ! ip multicast-routing ! ! ! ! ! ! interface FastEthernet0/0 ip address 10.1.2.1 255.255.255.0 ip pim sparse-mode ip cgmp duplex full ! interface Serial1/0 no ip address encapsulation frame-relay serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/0.605 point-to-point ip address 10.2.4.1 255.255.255.0 ip pim sparse-mode frame-relay interface-dlci 605 ! interface Serial1/0.609 point-to-point ip address 10.2.3.2 255.255.255.0 ip pim sparse-mode frame-relay interface-dlci 609 ! interface Serial1/1 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/2 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/3 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Ethernet2/0 no ip address shutdown duplex half ! interface Ethernet2/1 no ip address shutdown duplex half ! interface Ethernet2/2 no ip address shutdown duplex half ! interface Ethernet2/3 no ip address shutdown duplex half ! router ospf 10 log-adjacency-changes network 10.1.2.0 0.0.0.255 area 0 network 10.2.3.0 0.0.0.255 area 0 network 10.2.4.0 0.0.0.255 area 0 ! ip classless no ip http server no ip http secure-server ! ! ip pim rp-address 10.224.1.1 ! logging alarm informational ! ! ! ! control-plane ! ! ! ! ! ! gatekeeper shutdown ! ! line con 0 exec-timeout 0 0 stopbits 1 line aux 0 stopbits 1 line vty 0 4 login ! ! End R5#sh running-config Building configuration... Current configuration : 1601 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R5 ! boot-start-marker boot-end-marker ! ! no aaa new-model ! resource policy ! ip subnet-zero ip cef ! ! ! ! ip multicast-routing ! ! ! interface FastEthernet0/0 ip address 10.1.2.25 255.255.255.0 ip pim sparse-mode ip cgmp duplex full ! interface Serial1/0 no ip address encapsulation frame-relay serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/0.705 point-to-point ip address 10.2.5.1 255.255.255.0 ip pim sparse-mode frame-relay interface-dlci 705 ! interface Serial1/1 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/2 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Serial1/3 no ip address shutdown serial restart-delay 0 no dce-terminal-timing-enable ! interface Ethernet2/0 no ip address shutdown duplex half ! interface Ethernet2/1 no ip address shutdown duplex half ! interface Ethernet2/2 no ip address shutdown duplex half ! interface Ethernet2/3 no ip address shutdown duplex half ! router ospf 10 log-adjacency-changes network 10.1.2.0 0.0.0.255 area 0 network 10.2.5.0 0.0.0.255 area 0 ! ip classless no ip http server no ip http secure-server ! ! ip pim rp-address 10.224.1.1 ! logging alarm informational ! ! ! ! control-plane ! ! ! ! ! ! gatekeeper shutdown ! ! line con 0 exec-timeout 0 0 stopbits 1 line aux 0 stopbits 1 line vty 0 4 login ! ! end R5#

如同上面的實驗同樣，打開組播工具，進行發送和接收，使用show查查看其狀態。

R1#sh ip mroute IP Multicast Routing Table Flags: 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 - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group Outgoing interface flags: H - Hardware switched, A - Assert winner Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 224.0.1.40), 00:30:15/00:02:44, RP 10.224.1.1, flags: SJCL Incoming interface: Serial1/0.309, RPF nbr 10.2.2.2 Outgoing interface list: FastEthernet0/0, Forward/Sparse, 00:26:08/00:02:44 (*, 228.13.20.216), 00:06:29/stopped, RP 10.224.1.1, flags: SJCF Incoming interface: Serial1/0.309, RPF nbr 10.2.2.2 Outgoing interface list: FastEthernet0/0, Forward/Sparse, 00:06:29/00:02:40 (10.1.1.88, 228.13.20.216), 00:06:29/00:03:26, flags: FT Incoming interface: FastEthernet0/0, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.305, Forward/Sparse, 00:06:22/00:03:03 (*, 239.255.255.250), 00:29:34/00:02:42, RP 10.224.1.1, flags: SJC Incoming interface: Serial1/0.309, RPF nbr 10.2.2.2 Outgoing interface list: FastEthernet0/0, Forward/Sparse, 00:26:48/00:02:42 R2#sh ip mroute 228.13.20.216 IP Multicast Routing Table Flags: 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 - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group Outgoing interface flags: H - Hardware switched, A - Assert winner Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 228.13.20.216), 00:07:10/stopped, RP 10.224.1.1, flags: SP Incoming interface: Serial1/0.506, RPF nbr 10.2.4.1 Outgoing interface list: Null (10.1.1.88, 228.13.20.216), 00:07:10/00:03:25, flags: T Incoming interface: Serial1/0.503, RPF nbr 10.2.1.1 Outgoing interface list: Serial1/0.507, Forward/Sparse, 00:07:10/00:03:12 R3#sh ip mroute IP Multicast Routing Table Flags: 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 - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group Outgoing interface flags: H - Hardware switched, A - Assert winner Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 224.0.1.40), 00:31:22/00:03:28, RP 10.224.1.1, flags: SJCL Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.906, Forward/Sparse, 00:25:18/00:03:07 Serial1/0.903, Forward/Sparse, 00:25:47/00:03:28 (*, 228.13.20.216), 00:08:05/00:03:17, RP 10.224.1.1, flags: S Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.903, Forward/Sparse, 00:08:05/00:03:17 (10.1.1.88, 228.13.20.216), 00:08:05/00:02:55, flags: PT Incoming interface: Serial1/0.903, RPF nbr 10.2.2.1 Outgoing interface list: Null (*, 239.255.255.250), 00:25:47/00:03:02, RP 10.224.1.1, flags: S Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0.906, Forward/Sparse, 00:03:15/00:03:02 Serial1/0.903, Forward/Sparse, 00:25:47/00:02:30 R4#sh ip mroute IP Multicast Routing Table Flags: 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 - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group Outgoing interface flags: H - Hardware switched, A - Assert winner Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 224.0.1.40), 00:32:06/00:02:50, RP 10.224.1.1, flags: SJCL Incoming interface: Serial1/0.609, RPF nbr 10.2.3.1 Outgoing interface list: FastEthernet0/0, Forward/Sparse, 00:02:04/00:01:25 Serial1/0.605, Forward/Sparse, 00:24:34/00:03:12 (*, 228.13.20.216), 00:08:44/00:02:51, RP 10.224.1.1, flags: SP Incoming interface: Serial1/0.609, RPF nbr 10.2.3.1 Outgoing interface list: Null (*, 239.255.255.250), 00:31:21/00:02:54, RP 10.224.1.1, flags: SJC Incoming interface: Serial1/0.609, RPF nbr 10.2.3.1 Outgoing interface list: FastEthernet0/0, Forward/Sparse, 00:03:59/00:01:28 R5#sh ip mroute IP Multicast Routing Table Flags: 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 - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel, z - MDT-data group sender, Y - Joined MDT-data group, y - Sending to MDT-data group Outgoing interface flags: H - Hardware switched, A - Assert winner Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, 224.0.1.40), 00:32:47/00:02:06, RP 10.224.1.1, flags: SJPCL Incoming interface: FastEthernet0/0, RPF nbr 10.1.2.1 Outgoing interface list: Null (*, 228.13.20.216), 00:09:29/stopped, RP 10.224.1.1, flags: SJPC Incoming interface: FastEthernet0/0, RPF nbr 10.1.2.1 Outgoing interface list: Null (10.1.1.88, 228.13.20.216), 00:09:28/00:02:57, flags: JT Incoming interface: Serial1/0.705, RPF nbr 10.2.5.2 Outgoing interface list: FastEthernet0/0, Forward/Sparse, 00:09:28/00:02:07, A (*, 239.255.255.250), 00:32:06/00:02:09, RP 10.224.1.1, flags: SJPC Incoming interface: FastEthernet0/0, RPF nbr 10.1.2.1 Outgoing interface list: Null R5#sh ip route 10.224.1.1 Routing entry for 10.224.1.1/32 Known via "ospf 10", distance 110, metric 66, type intra area Last update from 10.1.2.1 on FastEthernet0/0, 00:33:44 ago Routing Descriptor Blocks: * 10.1.2.1, from 10.2.3.1, 00:33:44 ago, via FastEthernet0/0 Route metric is 66, traffic share count is 1 R5#sh ip route 10.1.1.0 Routing entry for 10.1.1.0/24 Known via "ospf 10", distance 110, metric 129, type intra area Last update from 10.2.5.2 on Serial1/0.705, 00:33:55 ago Routing Descriptor Blocks: * 10.2.5.2, from 10.2.2.1, 00:33:55 ago, via Serial1/0.705 Route metric is 129, traffic share count is 1 R4#sh ip pim interface Address Interface Ver/ Nbr Query DR DR Mode Count Intvl Prior 10.1.2.1 FastEthernet0/0 v2/S 1 30 1 10.1.2.25 10.2.4.1 Serial1/0.605 v2/S 1 30 1 0.0.0.0 10.2.3.2 Serial1/0.609 v2/S 1 30 1 0.0.0.0

未完等續。。。。