BFD协议原理及应用

1、0网络发展需求和现状网络发展需求和现状l快速检测相邻系统之间的通信故障，并快速检测相邻系统之间的通信故障，并切换到备份路径是可靠网络的必备功能；切换到备份路径是可靠网络的必备功能；l采用采用“慢慢Hello”机制的控制协议检测时机制的控制协议检测时间以秒为单位，无法实现快速检测；间以秒为单位，无法实现快速检测；l控制协议一般只能完成控制层面的检测，控制协议一般只能完成控制层面的检测，无法做到对转发层面的快速检测；无法做到对转发层面的快速检测；l一些硬件检测可以快速发现转发故障一些硬件检测可以快速发现转发故障（如（如SDH），但并不是所有介质都支持），但并不是所有介质都支持这样的硬件检测。这样的

2、硬件检测。1BFD的诞生的诞生l一种通用的检测邻居间转发路径可用性一种通用的检测邻居间转发路径可用性的协议呼之欲出的协议呼之欲出lBFD（Bidirectional Forwarding Detection）双向转发检测诞生）双向转发检测诞生IETF标准 RFC5880专注于故障快速检测，且轻负荷专注于转发平面检测与传输介质和底层协议无关为上层控制协议提供检测服务，自身不作为无发现机制，由上层协议提供邻居信息n BFD的诞生的诞生n BFD协议原理协议原理n BFD协议典型协议典型应用应用n BFD配置问题探讨配置问题探讨目录目录3BFD会话的触发会话的触发lBFD会话的触发过程会话的触发过程

3、上层协议如OSPF发现邻居OSPF通知BFD与邻居建立会话BFD向邻居建立会话OSPF PeersBFD PeersOSPF informsBFD the 4BFD邻居的角色邻居的角色lBFD邻居角色邻居角色Active: 可以主动发起会话建立Passive：不可以主动发起会话，被动接受；How are you?FineHow are you?Fine!ActiveActiveActiveP5BFD会话的建立和拆除会话的建立和拆除三次握手三次握手lBFD会话建立和拆除都是三次握手会话建立和拆除都是三次握手DownDown - InitBFD DownInit - UpABBFD InitBFD

4、 UpInit - UpDownUp- DownBFD DownUp- DownBFD DownBFD DownDownD6BFD的操作模式的操作模式lBFD有两种操作模式有两种操作模式异步模式（ Asynchronous ）查询模式（Demand）UpUpIm alive!Im alive too!UpU7BFD的辅助功能的辅助功能EcholBFD的回声功能同样可以实现双向检测的回声功能同样可以实现双向检测需要邻居双方都支持在任何一个方向可选使能仅在UP状态发送EchoHi!8BFD会话会话Down通知通知lBDF会话会话Down后通知上层协议采取动作后通知上层协议采取动作OSPF neig

5、hbor relationship is overBFD detects failure, session state becomes DOWNBFD informsOSPF, the peeris 9BFD重要参数重要参数l定时器定时器min-transmit-interval， BFD 控制报文的最小发送时间min-echo-receive-interval，系统接收 BFD echo 报文的最小时间间隔min-receive-interval， BFD 控制报文的最小接收时间间隔detect-multiplier， BFD 报文最大失效的个数lEcho源地址源地址echo-source-

6、ip， BFD echo 报文源IP 地址n BFD的诞生的诞生n BFD协议原理协议原理n BFD应用举例应用举例n BFD配置问题探讨配置问题探讨目录目录11BFD典型应用概述典型应用概述lBFD与静态路由联动与静态路由联动lBFD与动态路由协议联动与动态路由协议联动lBFD与与MPLS联动联动lBFD与与Track联动联动12BFD与与Track联动联动lBDF与与Track联动实现联动实现VRRP快速倒换快速倒换SmartBitsS95E-1Vlan100: 100.1.1.1Vlan 10: 10.1.1.14/0/234/0/234/0/164/0/16VRRP: 100.1.1.

7、254Vlan100: 100.1.1.2S95E-2Vlan 10: 10.1.1.2Port1/1: 100.1.1.3Port1/2: 10.1.1.3Port1/3: 10.1.1.31/0/11/0/13测试步骤和预期结果测试步骤和预期结果l测试步骤测试步骤从SMB的Port 1向10.1.1.3的地址发包，经过VRRP组转发后，由SMB的Port 2或Port 3收到；在没有启用BFD检测的情况下，测试VRRP的Master故障造成的中断时间；在启用了BFD检测，并与Track和VRRP联动的情况下，测试VRRP的Master故障造成的中断时间；l预期结果预期结果没有启用BFD时，

8、中断时间为秒级启用BFD后，中断时间为毫秒级14BFD相关配置相关配置l配置配置BFDbfd echo-source-ip 1.1.1.1interface Vlan-interface100bfd min-echo-receive-interval 10bfd detect-multiplier 3l配置配置Track联动联动track 10 bfd echo interface Vlan-interface100 remote ip 100.1.1.1 local ip 100.1.1.2l配置配置VRRP联动联动vrrp vrid 1 track 10 15测试数据测试数据Test1Te

9、st2Test3Test4Test5Test6Port 1267155316132033019819235476123829522110861Port 2836384470042627105931000632461900139Port 315151958188042054057141983517469521207032发包速率(p/ms)100100100100100100中断时间(ms)16测试结论测试结论l测试结论：测试结论：没有启用BFD时，VRRP的Master故障，VRRP备份组通过协议自己的Hello机制检测故障。中断时间约为3秒。启用BFD时，通过 Track与VRRP联动， V

10、RRP的Master故障后，BFD首先发现线路中断，随即通知Track。Track启动Switchover的动作，将原Slave切换成新的Master。中断时间约为30多毫秒；通过使用BFD协议，VRRP备份组对转发路径故障的感应灵敏度大大的提高了，故障造成的中断时间也由秒级达到毫秒级，实现了VRRP的快速倒换。17n BFD的诞生的诞生n BFD协议原理协议原理n BFD应用举例应用举例n BFD配置问题探讨配置问题探讨目录目录18SMBG5/0/1G5/0/1VLAN100G5/0/2Port1Port2G5/0/2S125_1S125_2测试一、拓扑及设备配置l 关键配置：关键配置：两个

11、千兆电口聚合,在三层接口上启用OSPF BFD功能；启用ospf功能，把两端的Loopback地址3.3.3.3和4.4.4.4引入到ospf中；OSPF PeerBFD PeerL1：3.3.3.3L1：19测试一、链路聚合/BFD/OSPF 状态125-1-Vlan-interface100display link-aggregation verbose Local: Port Status Priority Oper-Key Flag - GE5/0/1 S 32768 1 ACDEF GE5/0/2 S 32768 1 ACDEFRemote: Actor Partner Priori

12、ty Oper-Key SystemID Flag - GE5/0/1 9 32768 1 0 x8000, 0023-893d-1c00 ACDEF GE5/0/2 10 32768 1 0 x8000, 0023-893d-1c00 ACDEF125-1-Vlan-interface100display bfd session LD/RD SourceAddr DestAddr State Holdtime Interface 4/4 1.1.1.1 1.1.1.2 Up 600ms Vlan100125-1-Vlan-interface100dis ip router-tableRout

13、ing Tables: Public Destinations : 6 Routes : 6Destination/Mask Proto Pre Cost NextHop Interface4.4.4.4/32 O_ASE 150 1 1.1.1.2 V20SMBG5/0/1G5/0/1VLAN100G5/0/2Port1Port2G5/0/2S125_1S125_2测试一、Shutdown其中一个端口l shutdown其中一个端口：其中一个端口：125-2-GigabitEthernet5/0/1shutdownX21测试一、测试结果125-1-Vlan-interface100ping

14、-c 1000 4.4.4.4 PING 4.4.4.4: 56 data bytes, press CTRL_C to break Reply from 4.4.4.4: bytes=56 Sequence=34 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=35 ttl=255 time=1 ms%Sep 2 19:38:11:269 2010 125-1 BFD/4/LOG:Sess1.1.1.1/1.1.1.2,Vlan100,Ctrl, Sta: UP-DOWN, Diag: 5%Sep 2 19:38:11:381

15、2010 125-1 RM/3/RMLOG:OSPF-NBRCHANGE: Process 1, Neighbor 1.1.1.2(Vlan-interface100) from Full to Down Request time out%Sep 2 19:38:12:969 2010 125-1 IFNET/4/LINK UPDOWN: GigabitEthernet5/0/1: link status is DOWN Reply from 4.4.4.4: bytes=56 Sequence=37 ttl=255 time=1 ms%Sep 2 19:38:13:080 2010 125-

16、1 LAGG/2/LAGG_LOG: Port member GigabitEthernet5/0/1 of aggregation group BAGG1 becomes INACTIVE, because the ports configuration is improper for aggregation. Reply from 4.4.4.4: bytes=56 Sequence=38 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=39 ttl=255 time=1 ms Reply from 4.4.4.4: byte

17、s=56 Sequence=40 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=41 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=42 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=43 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=44 ttl=255 time=1 ms Request time out Request time

18、 out Request time out%Sep 2 19:38:15:175 2010 125-1 RM/3/RMLOG:OSPF-NBRCHANGE: Process 1, Neighbor 1.1.1.2(Vlan-interface100) from Loading to Full Reply from 4.4.4.4: bytes=56 Sequence=45 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=46 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequen

19、ce=47 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=48 ttl=255 time=1 ms%Sep 2 19:38:16:200 2010 125-1 BFD/4/LOG:Sess1.1.1.1/1.1.1.2,Vlan100,Ctrl, Sta: DOWN-UP, Diag: 0Reply from 4.4.4.4: bytes=56 Sequence=52 ttl=255 time=1 22测试一、进一步测试（1）l 更改配置更改配置：更改BFD检测时间为900ms；测试结果正常。125-1-Vlan-interfa

20、ce100ping -c 1000 4.4.4.4 PING 4.4.4.4: 56 data bytes, press CTRL_C to break Reply from 4.4.4.4: bytes=56 Sequence=34 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=35 ttl=255 time=1 ms Request time out%Sep 2 19:38:12:969 2010 125-1 IFNET/4/LINK UPDOWN: GigabitEthernet5/0/1: link status is

21、DOWN Reply from 4.4.4.4: bytes=56 Sequence=37 ttl=255 time=1 ms%Sep 2 19:38:13:080 2010 125-1 LAGG/2/LAGG_LOG: Port member GigabitEthernet5/0/1 of aggregation group BAGG1 becomes INACTIVE, because the ports configuration is improper for aggregation. Reply from 4.4.4.4: bytes=56 Sequence=38 ttl=255 t

22、ime=1 ms Reply from 4.4.4.4: bytes=56 Sequence=39 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=40 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=41 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=42 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=43 ttl=255 time=1

23、 ms Reply from 4.4.4.4: bytes=56 Sequence=44 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=45 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=46 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=47 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=48 ttl=255 time=1 23测试

24、一、进一步测试（2）l 更改配置更改配置：删除BFD功能；测试结果正常。125-1-Vlan-interface100ping -c 1000 4.4.4.4 PING 4.4.4.4: 56 data bytes, press CTRL_C to break Reply from 4.4.4.4: bytes=56 Sequence=26 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=27 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=28 ttl=255 ti

25、me=1 ms Reply from 4.4.4.4: bytes=56 Sequence=29 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=30 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=31 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=32 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=33 ttl=255 time=1

26、ms Reply from 4.4.4.4: bytes=56 Sequence=34 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=35 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=36 ttl=255 time=1 ms%Sep 3 15:18:51:889 2010 125-1 IFNET/4/LINK UPDOWN: Ten-GigabitEthernet3/0/2: link status is DOWN %Sep 3 15:18:52:000 201

27、0 125-1 LAGG/2/LAGG_LOG: Port member Ten-GigabitEthernet3/0/2 of aggregation group BAGG1 becomes INACTIVE, because the ports configuration is improper for aggregation. Request time out Reply from 4.4.4.4: bytes=56 Sequence=38 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=39 ttl=255 time=1

28、ms Reply from 4.4.4.4: bytes=56 Sequence=40 ttl=255 time=1 ms 24SMBT3/0/2T3/0/2VLAN100T3/0/4Port1Port2T3/0/4S125_1S125_2测试二、拓扑及设备配置l 关键配置：关键配置：两个万兆光接口聚合,在三层接口上启用OSPF BFD功能；启用ospf功能，把两端的Loopback地址3.3.3.3和4.4.4.4引入到ospf中；OSPF PeerBFD PeerL1：3.3.3.3L1：25测试二、链路聚合/BFD/OSPF 状态125-1display link-aggregation

29、 verbose System ID: 0 x8000, 0023-893c-f800Local: Port Status Priority Oper-Key Flag - XGE3/0/2 S 32768 1 ACDEF XGE3/0/4 S 32768 1 ACDEFRemote: Actor Partner Priority Oper-Key SystemID Flag - XGE3/0/2 107 32768 1 0 x8000, 0023-893d-1c00 ACDEF XGE3/0/4 108 32768 1 0 x8000, 0023-893d-1c00 ACDEF125-1di

30、sp125-1display bfd sessionLD/RD SourceAddr DestAddr State Holdtime Interface 11/11 1.1.1.1 1.1.1.2 Up 20ms Vlan100125-1disp ip rouDestination/Mask Proto Pre Cost NextHop Interface4.4.4.4/32 O_ASE 150 1 1.1.1.2 V26测试二、测试结果125-1-Vlan-interface100ping -c 10000 4.4.4.4 PING 4.4.4.4: 56 data bytes, press

31、 CTRL_C to breakReply from 4.4.4.4: bytes=56 Sequence=330 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=331 ttl=255 time=1 ms%Sep 3 09:05:54:662 2010 125-1 IFNET/4/LINK UPDOWN: Ten-GigabitEthernet3/0/2: link status is DOWN %Sep 3 09:05:54:774 2010 125-1 LAGG/2/LAGG_LOG: Port member Ten-Gig

32、abitEthernet3/0/2 of aggregation group BAGG1 becomes INACTIVE, because the ports configuration is improper for aggregation. Request time out Reply from 4.4.4.4: bytes=56 Sequence=333 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=334 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=335 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=336 ttl=255 time=1 ms Reply from 4.4.4.4: bytes=56 Sequence=337 tt