第三章 PIM稀疏（雙向）模式.doc

第三章 PIM稀疏（雙向）模式PIM稀疏（雙向）模式是PIM稀疏模式的擴(kuò)展，PIM稀疏模式不能朝上游方向傳輸數(shù)據(jù)包，這將和所有的組播路由器所執(zhí)行的RPF檢查相沖突。只有當(dāng)所有其他流量在共享樹中通過RP向下流動時(shí)，所有加入信息才會包含在注冊信息中發(fā)給RP。雙向PIM需指定一個(gè)轉(zhuǎn)發(fā)路由器（DF）來避免組播拓?fù)涞沫h(huán)路，每一個(gè)網(wǎng)段均需選舉一個(gè)DF，負(fù)責(zé)將適當(dāng)?shù)慕M播流量向上游轉(zhuǎn)發(fā)，對RP具有最佳路由的路由器成為DF。具體一點(diǎn)來說PIM稀疏雙向模式適用在一個(gè) Many-to-Many的環(huán)境，這種環(huán)境下如采用PIM稀疏模式，會產(chǎn)生大量的（S，G）路由，采用PIM雙向模式最顯著的特點(diǎn)就是可以減少路由表的條目。改用雙向模式之后，基本可以這么認(rèn)為，所有從源發(fā)出的組播數(shù)據(jù)包逐跳向RP的方向傳遞，到達(dá)RP之后，逐跳向組播接收客戶端方向傳遞，因此RP最好位于網(wǎng)絡(luò)的核心位置，否之可能出現(xiàn)次優(yōu)路徑選擇。接上個(gè)實(shí)驗(yàn)拓?fù)洌?） 所有PIM稀疏模式路由器啟用雙向支持R1 R2 R3 R4 R5 全局配置命令I(lǐng)p pim bidir-enableIp pim rp-address 1.1.1.1 bidir2) RP地址所在的接口需運(yùn)行PIM稀疏模式，否之不安裝下游的組注冊信息。R1(config)#int lo0R1(config-if)#ip pim sparse-mode我們把R2 R3 R4充當(dāng)組的接收者，而R4 R5充當(dāng)源的發(fā)送者，R5有1個(gè)接收口地址充當(dāng)源，R2有2個(gè)接口地址充當(dāng)源。將R2 R3 加入組R2(config)#int lo0R2(config-if)#ip igmp join-group 238.1.1.1R2(config-if)#ip pim sparse-modeR3(config)#int lo0R3(config-if)#ip igmp join-group 238.1.1.1R3(config-if)#ip pim sparse-mode在R4 R5分別ping組地址，不指定發(fā)送源地址的情況下，所有運(yùn)行PIM稀疏模式的接口地址均會作為源地址。R5#ping Protocol ip: Target IP address: 238.1.1.1Repeat count 1: Datagram size 100: Timeout in seconds 2: Extended commands n: Sweep range of sizes n: Type escape sequence to abort.Sending 1, 100-byte ICMP Echos to 238.1.1.1, timeout is 2 seconds:Reply to request 0 from 35.1.1.3, 20 ms R3的應(yīng)答Reply to request 0 from 24.1.1.4, 108 ms R4的應(yīng)答Reply to request 0 from 12.1.1.2, 52 ms R2的應(yīng)答R4#ping Protocol ip: Target IP address: 238.1.1.1Repeat count 1: 100Datagram size 100: Timeout in seconds 2: Extended commands n: Sweep range of sizes n: Type escape sequence to abort.Sending 1, 100-byte ICMP Echos to 238.1.1.1, timeout is 2 seconds:Reply to request 0 from 4.4.4.4, 40 msReply to request 0 from 13.1.1.3, 168 msReply to request 0 from 13.1.1.3, 92 msReply to request 0 from 24.1.1.2, 92 msReply to request 0 from 24.1.1.2, 72 ms看一下R2 R3的組播路由表R2#sh 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 - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, s - SSMOutgoing interface flags: H - Hardware switchedTimers: Uptime/ExpiresInterface state: Interface, Next-Hop or VCD, State/Mode(*, 238.1.1.1), 00:05:28/00:00:00, RP 1.1.1.1, flags: BCL Bidir-Upstream: Serial2/0, RPF nbr 12.1.1.1 Outgoing interface list: Serial1/0, Forward/Sparse, 00:04:28/00:03:07 Loopback0, Forward/Sparse, 00:05:09/00:02:20 Serial2/0, Bidir-Upstream/Sparse, 00:05:28/00:00:00以下輸入省略R3#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 - Candidate for MSDP Advertisement, U - URD, I - Received Source Specific Host Report, s - SSMOutgoing interface flags: H - Hardware switchedTimers: Uptime/ExpiresInterface state: Interface, Next-Hop or VCD, State/Mode(*, 224.0.1.40), 00:06:16/00:00:00, RP 1.1.1.1, flags: BCL Bidir-Upstream: Serial1/0, RPF nbr 13.1.1.1 Outgoing interface list: Serial2/0, Forward/Sparse, 00:05:46/00:02:52 Serial1/0, Bidir-Upstream/Sparse, 00:06:13/00:00:00(*, 238.1.1.1), 00:05:39/00:00:00, RP 1.1.1.1, flags: BCL Bidir-Upstream: Serial1/0, RPF nbr 13.1.1.1 Outgoing interface list: