stp生成樹(shù)協(xié)議培訓(xùn)

1、1 2006, Shenzhen Polytechnic. All rights reserved.生成樹(shù)生成樹(shù)協(xié)議協(xié)議Spanning Tree Protocol2 2 2 2006, Shewzhen Polytechnic. All rights reserved.Objectives Redundant topologies Spanning Tree Protocol3 3 3 2006, Shewzhen Polytechnic. All rights reserved.冗余（冗余（Redundancy）冗余網(wǎng)絡(luò)拓?fù)浯_保網(wǎng)絡(luò)持續(xù)工作，避免單點(diǎn)故障冗余網(wǎng)絡(luò)拓?fù)浯_保網(wǎng)絡(luò)持續(xù)工作，避免單

2、點(diǎn)故障Redundant networking topologies are designed to ensure that networks continue to function in the presence of single points of failure. 4 4 4 2006, Shewzhen Polytechnic. All rights reserved.冗余拓?fù)洌ㄈ哂嗤負(fù)洌≧edundant Topologies）5 5 5 2006, Shewzhen Polytechnic. All rights reserved.冗余拓?fù)洌ㄈ哂嗤負(fù)洌≧edundant Top

3、ologies） 1.冗余拓?fù)涞哪繕?biāo)是為了避免網(wǎng)絡(luò)出現(xiàn)單點(diǎn)故障冗余拓?fù)涞哪繕?biāo)是為了避免網(wǎng)絡(luò)出現(xiàn)單點(diǎn)故障 A goal of redundant topologies is to eliminate network outages caused by a single point of failure. 2.所有的網(wǎng)絡(luò)需要冗余來(lái)提高可靠性所有的網(wǎng)絡(luò)需要冗余來(lái)提高可靠性 All networks need redundancy for enhanced reliability.6 6 6 2006, Shewzhen Polytechnic. All rights reserved.簡(jiǎn)單的冗余交換

4、拓?fù)浜?jiǎn)單的冗余交換拓?fù)洌⊿imple Redundant Switched Topology）7 7 7 2006, Shewzhen Polytechnic. All rights reserved.簡(jiǎn)單的冗余交換拓?fù)浜?jiǎn)單的冗余交換拓?fù)洌⊿imple Redundant Switched Topology） 1.冗余拓?fù)湎藛吸c(diǎn)故障冗余拓?fù)湎藛吸c(diǎn)故障 Redundant topologies eliminate single points of failure. 2. 交換機(jī)對(duì)不知道地址的幀進(jìn)行泛洪交換機(jī)對(duì)不知道地址的幀進(jìn)行泛洪 Switches will flood frames f

5、or unknown destinations. 3.交換機(jī)對(duì)廣播和組播也進(jìn)行泛洪。交換機(jī)對(duì)廣播和組播也進(jìn)行泛洪。 Broadcasts and multicasts are also flooded. 4.冗余交換拓?fù)浠蛟S會(huì)帶來(lái)廣播風(fēng)暴、多幀拷貝以及冗余交換拓?fù)浠蛟S會(huì)帶來(lái)廣播風(fēng)暴、多幀拷貝以及MAC地址表不地址表不穩(wěn)定的問(wèn)題穩(wěn)定的問(wèn)題 A redundant switched topology may cause broadcast storms, multiple frame copies, and MAC address table instability problems.8 8 8

6、2006, Shewzhen Polytechnic. All rights reserved.廣播風(fēng)暴（廣播風(fēng)暴（Broadcast Storm）9 9 9 2006, Shewzhen Polytechnic. All rights reserved.多幀傳輸（多幀傳輸（Multiple Frame Transmissions）在冗余交換網(wǎng)絡(luò)中，對(duì)終端設(shè)備來(lái)講，收到多幀相同數(shù)據(jù)是可能的。在冗余交換網(wǎng)絡(luò)中，對(duì)終端設(shè)備來(lái)講，收到多幀相同數(shù)據(jù)是可能的。In a redundant switched network it is possible for an end device to recei

7、ve multiple frames. 101010 2006, Shewzhen Polytechnic. All rights reserved.創(chuàng)建邏輯無(wú)環(huán)路拓?fù)鋭?chuàng)建邏輯無(wú)環(huán)路拓?fù)洌–reating a logical loop free topology） 1.冗余增加了可靠性，但是同時(shí)將物理環(huán)路帶進(jìn)網(wǎng)絡(luò)。冗余增加了可靠性，但是同時(shí)將物理環(huán)路帶進(jìn)網(wǎng)絡(luò)。Reliability is increased by redundancy. redundancy connections introduce physical loops into the network. 2. 解決辦法就是創(chuàng)建邏輯

8、無(wú)環(huán)路拓?fù)?，同時(shí)保留物理環(huán)存在解決辦法就是創(chuàng)建邏輯無(wú)環(huán)路拓?fù)?，同時(shí)保留物理環(huán)存在 The solution is to allow physical loops, but create a loop free logical topology. 3.無(wú)環(huán)路拓?fù)浞Q為樹(shù)，并且是可擴(kuò)展的樹(shù)。無(wú)環(huán)路拓?fù)浞Q為樹(shù)，并且是可擴(kuò)展的樹(shù)。 The loop free logical topology created is called a tree. It is a spanning tree because all devices in the network are reachable or spanned

9、. 4.創(chuàng)建無(wú)環(huán)路拓?fù)涞乃惴ǚQ為生成樹(shù)算法。創(chuàng)建無(wú)環(huán)路拓?fù)涞乃惴ǚQ為生成樹(shù)算法。 The algorithm used to create this loop free logical topology is the spanning-tree algorithm. 111111 2006, Shewzhen Polytechnic. All rights reserved.STP術(shù)語(yǔ)（術(shù)語(yǔ)（STP Terms） 1. 橋橋ID (Bridge ID) 2. 開(kāi)銷(xiāo)（開(kāi)銷(xiāo)（Cost） 3. 橋協(xié)議數(shù)據(jù)單元（橋協(xié)議數(shù)據(jù)單元（BPDU）121212 2006, Shewzhen Polytechni

10、c. All rights reserved.橋橋ID (Bridge ID)1.BID用來(lái)識(shí)別每一個(gè)交換機(jī)用來(lái)識(shí)別每一個(gè)交換機(jī)/網(wǎng)橋。網(wǎng)橋。2.BID用來(lái)確定網(wǎng)絡(luò)的中心，在用來(lái)確定網(wǎng)絡(luò)的中心，在STP中稱為根橋。中稱為根橋。3.優(yōu)先級(jí)默認(rèn)為優(yōu)先級(jí)默認(rèn)為32768The BID consists of a bridge priority that defaults to 32768131313 2006, Shewzhen Polytechnic. All rights reserved.開(kāi)銷(xiāo)（開(kāi)銷(xiāo)（Cost） 最短路徑是最短路徑是cost累加，而累加，而cost是基于鏈路的速率的。是基于鏈路

11、的速率的。 Shortest path is based on cumulative link costs. Link costs are based on the speed of the link. 141414 2006, Shewzhen Polytechnic. All rights reserved.橋協(xié)議數(shù)據(jù)單元（橋協(xié)議數(shù)據(jù)單元（BPDU） 1.交換機(jī)發(fā)送的創(chuàng)建邏輯無(wú)環(huán)路的數(shù)據(jù)包稱為交換機(jī)發(fā)送的創(chuàng)建邏輯無(wú)環(huán)路的數(shù)據(jù)包稱為BPDU The message that a switch sends, allowing the formation of a loop free logic

12、al topology, is called a Bridge Protocol Data Unit (BPDU). 2.BPDU在阻塞的接口上也可以接收，這確保如果鏈路在阻塞的接口上也可以接收，這確保如果鏈路或設(shè)備出現(xiàn)問(wèn)題，新的生成樹(shù)會(huì)被計(jì)算或設(shè)備出現(xiàn)問(wèn)題，新的生成樹(shù)會(huì)被計(jì)算 BPDUs continue to be received on blocked ports. This ensures that if an active path or device fails, a new spanning tree can be calculated. 3.默認(rèn)，默認(rèn)，BPDU 2秒發(fā)送一次秒

13、發(fā)送一次 By default BPDUs are sent every two seconds.151515 2006, Shewzhen Polytechnic. All rights reserved.Spanning-Tree Protocol161616 2006, Shewzhen Polytechnic. All rights reserved.生成樹(shù)操作（生成樹(shù)操作（Spanning-Tree Operation）171717 2006, Shewzhen Polytechnic. All rights reserved.Spanning-Tree Operation(cont

14、.) 1.選舉根橋，選舉根橋，BID最小即是最小即是 Select a single switch that will act as the root of the spanning tree 2.計(jì)算自己到根橋距離計(jì)算自己到根橋距離 Calculate the shortest path from itself to the root switch 3.選擇根端口，距離根橋最近的接口選擇根端口，距離根橋最近的接口 Choose one of its ports as its root port, for each non-root switch. This is the interface

15、that gives the best path to the root switch. 4.選指定端口和非指定端口，非指定端口被阻塞。選指定端口和非指定端口，非指定端口被阻塞。 Select ports that are part of the spanning tree, the designated ports. Non-designated ports are blocked. 181818 2006, Shewzhen Polytechnic. All rights reserved.生成樹(shù)操作規(guī)則（生成樹(shù)操作規(guī)則（Spanning-Tree Operation Rules） 1.每

16、個(gè)網(wǎng)絡(luò)只有一個(gè)根橋每個(gè)網(wǎng)絡(luò)只有一個(gè)根橋 One root bridge per network. 2.每個(gè)非根橋只有一個(gè)根端口每個(gè)非根橋只有一個(gè)根端口 One root port per nonroot bridge. 3.每個(gè)段只有一個(gè)指定端口每個(gè)段只有一個(gè)指定端口 One designated port per segment. 4.非指定端口不被使用非指定端口不被使用 Nondesignated ports are unused.191919 2006, Shewzhen Polytechnic. All rights reserved.STP實(shí)例（實(shí)例（STP Example）2020

17、20 2006, Shewzhen Polytechnic. All rights reserved.生成樹(shù)端口狀態(tài)（生成樹(shù)端口狀態(tài)（Spanning-Tree Port States）212121 2006, Shewzhen Polytechnic. All rights reserved.生成樹(shù)端口狀態(tài)（生成樹(shù)端口狀態(tài)（Spanning-Tree Port States） 1.在阻塞狀態(tài)，端口僅能接收在阻塞狀態(tài)，端口僅能接收BPDU,需要需要20秒改變這種秒改變這種狀態(tài)狀態(tài) In the blocking state, ports can only receive BPDUs. It m

18、ay take up to 20 seconds to change from this state. 2.在偵聽(tīng)狀態(tài)，交換機(jī)確定是否有到根橋的其它路徑。在偵聽(tīng)狀態(tài)，交換機(jī)確定是否有到根橋的其它路徑。該狀態(tài)持續(xù)該狀態(tài)持續(xù)15秒。在該狀態(tài)，用戶的數(shù)據(jù)不能轉(zhuǎn)發(fā)，也秒。在該狀態(tài)，用戶的數(shù)據(jù)不能轉(zhuǎn)發(fā)，也不能學(xué)習(xí)不能學(xué)習(xí)MAC地址。地址。 In listening state, switches determine if there are any other paths to the root bridge. the forward delay and lasts for 15 seconds. In

19、 the listening state, user data is not being forwarded and MAC addresses are not being learned. 222222 2006, Shewzhen Polytechnic. All rights reserved.生成樹(shù)端口狀態(tài)（生成樹(shù)端口狀態(tài)（Spanning-Tree Port States） 3.在學(xué)習(xí)狀態(tài)，用戶的數(shù)據(jù)不能轉(zhuǎn)發(fā)，但是可以學(xué)習(xí)在學(xué)習(xí)狀態(tài)，用戶的數(shù)據(jù)不能轉(zhuǎn)發(fā)，但是可以學(xué)習(xí)MAC地址，該狀態(tài)持續(xù)地址，該狀態(tài)持續(xù)15秒。秒。 In learning state user data is not

20、 forwarded, but MAC addresses are learned from any traffic that is seen. The learning state lasts for 15 seconds and is also called the forward delay. 4.在轉(zhuǎn)發(fā)狀態(tài)，用戶數(shù)據(jù)被轉(zhuǎn)發(fā)，在轉(zhuǎn)發(fā)狀態(tài)，用戶數(shù)據(jù)被轉(zhuǎn)發(fā)，MAC地址繼續(xù)學(xué)習(xí)，地址繼續(xù)學(xué)習(xí)，BPDU仍然工作。仍然工作。 In forwarding state user data is forwarded and MAC addresses continue to be learned. BP

21、DUs are still processed. 232323 2006, Shewzhen Polytechnic. All rights reserved.Case Study Refer to the exhibit. All switches have the default STP configuration and all links are Fast Ethernet. Which port on which switch will Spanning Tree place in blockingmode?242424 2006, Shewzhen Polytechnic. All

22、 rights reserved.Enabling Spanning Tree打開(kāi)生成樹(shù)協(xié)議打開(kāi)生成樹(shù)協(xié)議Switch(config)#spanning-tree vlan 200 Enables spanning tree on a specific VLAN 打開(kāi)特定打開(kāi)特定VLAN的生成樹(shù)協(xié)議的生成樹(shù)協(xié)議 默認(rèn)時(shí)，所有默認(rèn)時(shí)，所有VLAN的的STP都是開(kāi)啟的，因此以上命令可都是開(kāi)啟的，因此以上命令可以不配置以不配置252525 2006, Shewzhen Polytechnic. All rights reserved.Configuring the Root Bridge配置根橋配置

23、根橋Switch(config)#spanning-tree vlan 200 priority 4096 Lowers the spanning tree priority, forcing this switch to be the root bridge 把網(wǎng)橋的優(yōu)先級(jí)值降低，會(huì)使得網(wǎng)橋成為根橋把網(wǎng)橋的優(yōu)先級(jí)值降低，會(huì)使得網(wǎng)橋成為根橋262626 2006, Shewzhen Polytechnic. All rights reserved.Setting Port Cost and VLAN Port Cost設(shè)置端口的設(shè)置端口的cost值值Switch(config-if)#span

24、ning-tree cost 18 Configures the spanning tree port cost of an interface 配置端口的配置端口的cost值值Switch(config-if)#spanning-tree vlan 200 cost 17 Configures the spanning tree VLAN port cost of an interface for a specific VLAN 可以在端口下為某一特定的可以在端口下為某一特定的VLAN指定指定cost值值272727 2006, Shewzhen Polytechnic. All right

25、s reserved.Verifying STP檢查檢查STPASW11#show spanning-tree vlan 200VLAN0200 Spanning tree enabled protocol ieee Root ID Priority 49352 Address 0008.2199.2bc0 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 49352 (priority 49152 sys-id-ext 200) Address 0008.2199.2bc0 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Agin