BFD
1.BFD简介 2.静态路由调用BFD 3.OSPF调用BFD 4.VRRP调用BFD
BFD：Bidirectional Forwarding Detection 双向转发检查
作用：毫秒级故障检查，通常结合三层协议（如静态路由，VRRP，OSPF，BGP等）实现链路故障快速检查。
如图1:R1到达R2的2.2.2.2的路由有两条线路，有上面的链路带宽高，所以路由走上面的路线，
但是当在R2的一侧线路出现了故障，这时R1无法及时的感知线路出现故障，因此采用BFD进行快速检查，能在毫秒的时间内完成线路的切换。
１.静态BFD检查
#R1的配置
[Huawei]sysnam R1
[R1]inteface Ethernet0/0/1
[R1-Ethernet0/0/1]ip address 21.1.1.10 255.255.255.0
[R1-Ethernet0/0/1]quit
[R1]interface Ethernet0/0/0
[R1-Ethernet0/0/0]ip address 12.1.1.10 255.255.255.0
[R1-Ethernet0/0/0]quit
[R1]interface loopback 0
[R1-loopback0]ip address 1.1.1.1 32
[R1-loopback0]quit
[R1]bfd
[R1-bfd]quit
[R1]bfd 1 bind peer-ip 12.1.1.11 source-ip 12.1.1.10
[R1-bfd-session-1]discriminator local 2
[R1-bfd-session-1]discriminator remot 1
[R1-bfd-session-1]commit
[R1-bfd-session-1]quit
[R1]
[R1]ip route-static 2.2.2.2 32 21.1.1.11
[R1]ip route-static 2.2.2.2 32 12.1.1.11 pre 55 track bfd-session 1
#R2的配置
[Huawei]sysnam R2
[R2]inteface Ethernet0/0/1 //进入接口
[R2-Ethernet0/0/1]ip address 21.1.1.11 255.255.255.0 //配置接口IP地址
[R2-Ethernet0/0/1]quit
[R2]interface Ethernet0/0/0
[R2-Ethernet0/0/0]ip address 12.1.1.11 255.255.255.0
[R2-Ethernet0/0/0]quit
[R2]interface loopback 0
[R2-loopback0]ip address 2.2.2.2 32
[R2-loopback0]quit
[R2]bfd //全局使能BFD
[R2-bfd]quit
[R2]bfd 1 bind peer-ip 12.1.1.1 0 source-ip 12.1.1.11 . //创建BFD进程1
[R2-bfd-session-1]discriminator local 1 //本地标识，两台路由器的标识需要互相对称
[R2-bfd-session-1]discriminator remot 2 //远端便是
[R2-bfd-session-1]commit //提交BFD配置
[R2-bfd-session-1]quit
[R2]ip route-static 1.1.1.1 32 21.1.1.10
[R2]ip route-static 1.1.1.1 32 12.1.1.10 pre 55 track bfd-session 1 //在静态路由下调用BFD
[R2]
#R10查看配置的BFD
<R10>display bfd session static
Local Remote PeerIpAddr State Type InterfaceName
1 2 12.1.1.11 Up S_IP_PEER -Total UP/DOWN Session Number : 1/0
<R10>
#R10上查看BFD详细配置
<R10>display bfd session static verbose
Session MIndex : 256 (Multi Hop) State : Up Name : 1
Local Discriminator : 1 Remote Discriminator : 2
Session Detect Mode : Asynchronous Mode Without Echo Function
BFD Bind Type : Peer IP Address
Bind Session Type : Static
Bind Peer IP Address : 12.1.1.11
Bind Interface : -
Track Interface : -
Bind Source IP Address : 12.1.1.10
FSM Board Id : 0 TOS-EXP : 7
Min Tx Interval (ms) : 1000 Min Rx Interval (ms) : 1000
Actual Tx Interval (ms): 1000 Actual Rx Interval (ms): 1000
Local Detect Multi : 3 Detect Interval (ms) : 3000
Echo Passive : Disable Acl Number : -
Destination Port : 3784 TTL : 254
Proc Interface Status : Disable Process PST : Disable
WTR Interval (ms) : -
Active Multi : 3
Last Local Diagnostic : No Diagnostic
Bind Application : No Application Bind
Session TX TmrID : - Session Detect TmrID : -
Session Init TmrID : - Session WTR TmrID : -
Session Echo Tx TmrID : -
PDT Index : FSM-0 | RCV-0 | IF-0 | TOKEN-0
Session Description : -
Total UP/DOWN Session Number : 1/0
<R10>
２.动态BFD：OSPF调用BFD加速收敛
#R1的配置
[R1]interface Ethernet0/0/0
[R1-Ethernet0/0/0]ip address 12.1.1.1 24
[R1-Ethernet0/0/0]quit
[R1]interface Loopback0
[R1-loopback0]ip address 1.1.1.1 255.255.255.255
[R1-loopback0]quit
[R1]router id 1.1.1.1 //配置路由器Router-ID
[R1]ospf 10 //开启OSPF进程10
[R1-ospf-10]area 0 //进入OSPF进程10的区域0
[R1-ospf-10-0.0.0.0]network 12.1.1.0 0.0.0.255 / /在OSPF10的区域0下宣告路由
[R1-ospf-10-0.0.0.0]network 1.1.1.1 0.0.0.0
[R1-ospf-10-0.0.0.0]quit
[R1-ospf-10]quit
[R1]bfd //全局开启BFD检查功能
[R1-bfd]quit
[R1]ospf 10 //进入OSPF进程10
[R1-ospf-10]bfd all-interfaces enable //在OSPF下开启BFD检测
[R1-ospf-10]quit
[R1]
#R2的配置
[R2]interface Ethernet0/0/0
[R2-Ethernet0/0/0]ip address 12.1.1.1 24
[R2-Ethernet0/0/0]quit
[R2]interface Loopback0 //进入环回口
[R2-loopback0]ip address 1.1.1.1 255.255.255.255 //配置环回口的地址
[R2-loopback0]quit
[R2]router id 1.1.1.1
[R2]ospf 10
[R2-ospf-10]area 0
[R2-ospf-10-0.0.0.0]network 12.1.1.0 0.0.0.255
[R2-ospf-10-0.0.0.0]network 1.1.1.1 0.0.0.0
[R2-ospf-10-0.0.0.0]quit
[R2-ospf-10]quit
[R2]bfd //全局开启BFD检查
[R2-bfd]quit
[R2]ospf 10 //进入OSPF的10进程
[R2-ospf-10]bfd all-interfaces enable
[R2-ospf-10]quit
[R2]
＃R10下显示BFD的动态邻居
<R10>display bfd session dynamic
Local Remote PeerIpAddr State Type InterfaceName
8192 8192 21.1.1.11 Up D_IP_IF GigabitEthernet0/0/0
8193 8193 12.1.1.11 Up D_IP_IF GigabitEthernet0/0/1
Total UP/DOWN Session Number : 2/0
<R10>
#R10上配置BFD的详细信息
<R10>display bfd session all verbose
Session MIndex : 257 (One Hop) State : Up Name : dyn_8192
Local Discriminator : 8192 Remote Discriminator : 8192
Session Detect Mode : Asynchronous Mode Without Echo Function
BFD Bind Type : Interface(GigabitEthernet0/0/0)
Bind Session Type : Dynamic
Bind Peer IP Address : 21.1.1.11
NextHop Ip Address : 21.1.1.11
Bind Interface : GigabitEthernet0/0/0
FSM Board Id : 0 TOS-EXP : 7
Min Tx Interval (ms) : 1000 Min Rx Interval (ms) : 1000
Actual Tx Interval (ms): 1000 Actual Rx Interval (ms): 1000
Local Detect Multi : 3 Detect Interval (ms) : 3000
Echo Passive : Disable Acl Number : -
Destination Port : 3784 TTL : 255
Proc Interface Status : Disable Process PST : Disable
WTR Interval (ms) : -
Active Multi : 3
Last Local Diagnostic : No Diagnostic
Bind Application : OSPF
Session TX TmrID : - Session Detect TmrID : -
Session Init TmrID : - Session WTR TmrID : -
Session Echo Tx TmrID : -
PDT Index : FSM-0 | RCV-0 | IF-0 | TOKEN-0
Session Description : -
Session MIndex : 258 (One Hop) State : Up Name : dyn_8193
Local Discriminator : 8193 Remote Discriminator : 8193
Session Detect Mode : Asynchronous Mode Without Echo Function
BFD Bind Type : Interface(GigabitEthernet0/0/1)
Bind Session Type : Dynamic
Bind Peer IP Address : 12.1.1.11
NextHop Ip Address : 12.1.1.11
Bind Interface : GigabitEthernet0/0/1
FSM Board Id : 0 TOS-EXP : 7
Min Tx Interval (ms) : 1000 Min Rx Interval (ms) : 1000
Actual Tx Interval (ms): 1000 Actual Rx Interval (ms): 1000
Local Detect Multi : 3 Detect Interval (ms) : 3000
Echo Passive : Disable Acl Number : -
Destination Port : 3784 TTL : 255
Proc Interface Status : Disable Process PST : Disable
WTR Interval (ms) : -
Active Multi : 3
Last Local Diagnostic : No Diagnostic
Bind Application : OSPF
Session TX TmrID : - Session Detect TmrID : -
Session Init TmrID : - Session WTR TmrID : -
Session Echo Tx TmrID : -
PDT Index : FSM-1 | RCV-0 | IF-0 | TOKEN-0
Session Description : -
Total UP/DOWN Session Number : 2/0
<R10>
3.VRRP联动BFD
拓扑图拓扑图
具体配置：
#R10配置
[R10]interface GigabitEthernet0/0/0 //进入接口GigabitEthernet0/0/0
[R10-GigabitEthernet0/0/0]ip address 21.1.1.10 255.255.255.0 //配置接口IP地址
[R10-GigabitEthernet0/0/0]quit //退出接口
[R10]bfd
[R10-bfd]quit
[R10]bfd 5 bind peer-ip 112.1.1.12 source-ip 112.1.1.10 //配置静态BFD-5
[R10-bfd-session-5]discriminator local 100 //配置本地值100
[R10-bfd-session-5]discriminator remote 200 //配置远端值200
[R10-bfd-session-5]commit //提交BFD配置
[R10-bfd-session-5]quit
[R10]bfd bb bind peer-ip 112.1.1.12 source-ip 112.1.1.10 auto
[R10-bfd-session-bb]quit
[R10]
[R10]interface GigabitEthernet0/0/1
[R10-GigabitEthernet0/0/1]ip address 12.1.1.10 255.255.255.0
[R10-GigabitEthernet0/0/1]vrrp vrid 10 virtual-ip 12.1.1.1
[R10-GigabitEthernet0/0/1]vrrp vrid 10 priority 105
[R10-GigabitEthernet0/0/1]vrrp vrid 10 track bfd-session 100//VRRP调用BFD100是BFD的本地标识
[R10-GigabitEthernet0/0/1]quit
[R10]interface loopback 0
[R10-loopback0]ip address 10.10.10.10 255.255.255.25
[R10-loopback0]quit
[R10]
#R11的配置
[R11]interface GigabitEthernet0/0/0
[R11-GigabitEthernet0/0/0]ip address 21.1.1.11 255.255.255.0
[R11-GigabitEthernet0/0/0]quit
[R11]interface GigabitEthernet0/0/1
[R11-GigabitEthernet0/0/1]ip address 12.1.1.11 255.255.255.0
[R11-GigabitEthernet0/0/1]vrrp vrid 10 virtual-ip 12.1.1.1
[R11-GigabitEthernet0/0/1]quit
[R11]interface loopback 0
[R11-loopback0]ip address 11.11.11.11 255.255.255.25
[R11-loopback0]quit
[R11]
#R12的配置
[R12]interface GigabitEthernet0/0/0
[R12-GigabitEthernet0/0/0]ip address 112.1.1.12 255.255.255.0
[R12-GigabitEthernet0/0/0]quit
[R12]
[R12]bfd 5 bind peer-ip 112.1.1.12 source-ip 112.1.1.10
[R12-bfd-session-5]discriminator local 200 //配置BFD的本地标识
[R12-bfd-session-5]discriminator remote 100 //配置BFD的远端标识
[R12-bfd-session-5]commit //提交BFD的配置
[R12-bfd-session-5]quit
[R12]bfd bb bind peer-ip 112.1.1.10 source-ip 112.1.1.12 auto //配置BFD自动检测机制
[R12]interface loopback 0
[R12-loopback0]ip address 12.12.12.12 255.255.255.255
[R12-loopback0]quit
[R12]
R10上查看BFD会话
[R10]display bfd session all
Local Remote PeerIpAddr State Type InterfaceName
8192 8192 21.1.1.11 Up D_IP_IF GigabitEthernet0/0/0
8193 8193 12.1.1.11 Up D_IP_IF GigabitEthernet0/0/1
100 200 112.1.1.12 Up S_IP_PEER -
Total UP/DOWN Session Number : 3/0
[R10]
#R10上查看VRRP配置（断开链路后VRRP优先级发生变化）
<R10>display vrrp
GigabitEthernet0/0/1 | Virtual Router 10
State : Backup
Virtual IP : 12.1.1.1 Master IP : 12.1.1.11
PriorityRun : 95 PriorityConfig : 105
MasterPriority : 100 Preempt : YES Delay Time : 0 s
TimerRun : 1 s TimerConfig : 1 s
Auth type : NONE Virtual MAC : 0000-5e00-010a
Check TTL : YES Config type : normal-vrrp
Backup-forward : disable Track BFD : bb Priority reduced : 10
BFD-session state : DOWN Create time : 2020-03-29 14:35:24 UTC-08:00
Last change time : 2020-03-29 15:29:32 UTC-08:00
<R10>
#R10在对端链路回复后的优先级
<R10>display vrrp
GigabitEthernet0/0/1 | Virtual Router 10
State : Master
Virtual IP : 12.1.1.1 Master IP : 12.1.1.10
PriorityRun : 105 PriorityConfig : 105
MasterPriority : 105 Preempt : YES Delay Time : 0 s
TimerRun : 1 s TimerConfig : 1 s
Auth type : NONE Virtual MAC : 0000-5e00-010a
Check TTL : YES Config type : normal-vrrp
Backup-forward : disable Track BFD : bb Priority reduced : 10
BFD-session state : UP Create time : 2020-03-29 14:35:24 UTC-08:00
Last change time : 2020-03-29 15:37:00 UTC-08:00
<R10>
注意：VRRP联动BFD：通常如果VRRP的上联有二层设备隔离，此时可以借助BFD实现故障检测。