BFD与静态路由联动
静态路由联动原理
静态路由自身没有检测机制，当网络发生故障的时候，需要管理员介入。BFD与静态路由联动特性可为公网静态路由绑定BFD会话，利用BFD会话来检测静态路由所在链路的状态。
BFD与静态路由联动可为每条静态路由绑定一个BFD会话，当这条静态路由上绑定的BFD会话检测到链路故障（由Up转为Down）后，BFD会将故障上报路由管理系统，由路由管理模块将这条路由设置为“非激活”状态（此条路由不可用，从IP路由表中删除）。当这条静态路由上绑定的BFD会话成功建立或者从故障状态恢复后（由Down转为Up），BFD会上报路由管理模块，由路由管理模块将这条路由设置为“激活”状态（此路由可用，加入IP路由表）。
典型配置1
拓扑图如下：
目标：BFD与静态路由联动实现浮动路由。
场景：R1到23.23.23.23/32网络可通过R2到达，也可通过R3到达（交换机作为二层转发）。R2作为主用R3作为备用。R1到R2、R3之间由于不是直连链路，因此接口状态不会影响到静态路由的有效性，此时使用BFD进行检测，当检测失效时，使用备份静态路由进行数据转发。
配置步骤
基本IP编址
BFD配置
BFD与静态路由联动配置
验证
1.基本IP编址
[R1]interface GigabitEthernet 0/0/1
[R1-GigabitEthernet0/0/1]ip add 10.0.12.1 24
[R1-GigabitEthernet0/0/1]q
[R1]interface GigabitEthernet 0/0/2
[R1-GigabitEthernet0/0/2]ip add 10.0.13.1 24
[R1-GigabitEthernet0/0/2]q
[R1]interface LoopBack 0
[R1-LoopBack0]ip add 10.0.1.1 32
[R1-LoopBack0]q
[R2]interface GigabitEthernet 0/0/1
[R2-GigabitEthernet0/0/1]ip add 10.0.12.2 24
[R2-GigabitEthernet0/0/1]q
[R2]interface LoopBack 0
[R2-LoopBack0]ip add 23.23.23.23 32
[R2-LoopBack0]q
[R3]interface GigabitEthernet 0/0/1
[R3-GigabitEthernet0/0/1]ip add 10.0.13.2 24
[R3-GigabitEthernet0/0/1]q
[R3]interface LoopBack 0
[R3-LoopBack0]ip add 23.23.23.23 32
[R3-LoopBack0]q
2.BFD配置
#在主用路径上启用BFD，检测R1到R2接口。
[R1]bfd //全局启用BFD
[R1-bfd]q
[R1]bfd 1 bind peer-ip 10.0.12.2 source-ip 10.0.12.1 auto //配置BFD会话
[R1-bfd-session-1]commit
[R1-bfd-session-1]q
[R2]bfd
[R2-bfd]q
[R2]bfd 1 bind peer-ip 10.0.12.1 source-ip 10.0.12.2 auto
[R2-bfd-session-1]commit
[R2-bfd-session-1]q
#查看BFD会话信息
[R1]display bfd session all
--------------------------------------------------------------------------------
Local Remote PeerIpAddr State Type InterfaceName
--------------------------------------------------------------------------------
8192 8192 10.0.12.2 Up S_AUTO_PEER -
--------------------------------------------------------------------------------
Total UP/DOWN Session Number : 1/0
[R2]display bfd session all
--------------------------------------------------------------------------------
Local Remote PeerIpAddr State Type InterfaceName
--------------------------------------------------------------------------------
8192 8192 10.0.12.1 Up S_AUTO_PEER -
--------------------------------------------------------------------------------
Total UP/DOWN Session Number : 1/0
3.BFD与静态路由联动配置
#在R2和R3上配置去往R1环回的静态路由
[R2]ip route-static 10.0.0.0 8 10.0.12.1
[R3]ip route-static 10.0.0.0 8 10.0.13.1
[R2]display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 9 Routes : 9
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.0.0/8 Static 60 0 RD 10.0.12.1 GigabitEthernet0/0/1
[R3]display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 9 Routes : 9
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.0.0/8 Static 60 0 RD 10.0.13.1 GigabitEthernet0/0/1
#在R1上配置静态路由并联动BFD
[R1]ip route-static 0.0.0.0 0.0.0.0 10.0.12.2 track bfd-session 1 //默认主路由与bfd联动
[R1]ip route-static 0.0.0.0 0.0.0.0 10.0.13.2 preference 100 //备用路由调整优先级（静态路由默认60）
#查看路由表
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
0.0.0.0/0 Static 60 0 RD 10.0.12.2 GigabitEthernet0/0/1
//正常情况下主用路由加入转发表
[R1]display ip routing-table 0.0.0.0 0 verbose
Route Flags: R - relay, D - download to fib, T - to vpn-instance
------------------------------------------------------------------------------
Routing Table : Public
Summary Count : 2
Destination: 0.0.0.0/0
Protocol: Static Process ID: 0
Preference: 60 Cost: 0
NextHop: 10.0.12.2 Neighbour: 0.0.0.0
State: Active Adv Relied Age: 00h04m53s
Tag: 0 Priority: medium
Label: NULL QoSInfo: 0x0
IndirectID: 0x80000001
RelayNextHop: 0.0.0.0 Interface: GigabitEthernet0/0/1
TunnelID: 0x0 Flags: RD
Destination: 0.0.0.0/0
Protocol: Static Process ID: 0
Preference: 100 Cost: 0
NextHop: 10.0.13.2 Neighbour: 0.0.0.0
State: Inactive Adv Relied Age: 00h04m32s
Tag: 0 Priority: medium
Label: NULL QoSInfo: 0x0
IndirectID: 0x80000002
RelayNextHop: 0.0.0.0 Interface: GigabitEthernet0/0/2
TunnelID: 0x0 Flags: R
//备用路由此时为不活跃状态（不加表）
注意：如果不配置BFD检测的话，在R1上是没有任何机制可以判断静态路由是否有效的，因此BFD在这种场景非常重要。
4.配置验证
在R2上关闭连接至R1的端口，模拟主用路径故障。
#关闭R2端口
[R2]interface GigabitEthernet 0/0/1
[R2-GigabitEthernet0/0/1]shutdown
#R1到目的网络有短暂丢包（切换备用线路）
PING 23.23.23.23: 56 data bytes, press CTRL_C to break
Reply from 23.23.23.23: bytes=56 Sequence=1 ttl=255 time=2 ms
Reply from 23.23.23.23: bytes=56 Sequence=2 ttl=255 time=2 ms
Reply from 23.23.23.23: bytes=56 Sequence=3 ttl=255 time=1 ms
Reply from 23.23.23.23: bytes=56 Sequence=4 ttl=255 time=2 ms
Reply from 23.23.23.23: bytes=56 Sequence=5 ttl=255 time=2 ms
Reply from 23.23.23.23: bytes=56 Sequence=6 ttl=255 time=4 ms
Reply from 23.23.23.23: bytes=56 Sequence=7 ttl=255 time=1 ms
Request time out
Request time out
Reply from 23.23.23.23: bytes=56 Sequence=10 ttl=255 time=1 ms
Reply from 23.23.23.23: bytes=56 Sequence=11 ttl=255 time=8 ms
Reply from 23.23.23.23: bytes=56 Sequence=12 ttl=255 time=1 ms
#BFD状态down
--------------------------------------------------------------------------------
Local Remote PeerIpAddr State Type InterfaceName
--------------------------------------------------------------------------------
8192 0 10.0.12.2 Down S_AUTO_PEER -
--------------------------------------------------------------------------------
Total UP/DOWN Session Number : 0/1
#R1路由表（此时备用路由被加入路由转发表）
Route Flags: R - relay, D - download to fib, T - to vpn-instance
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
0.0.0.0/0 Static 100 0 RD 10.0.13.2 GigabitEthernet0/0/2
#R1默认路由信息（主用路由状态成为invalid，备用为active）
Route Flags: R - relay, D - download to fib, T - to vpn-instance
------------------------------------------------------------------------------
Routing Table : Public
Summary Count : 2
Destination: 0.0.0.0/0
Protocol: Static Process ID: 0
Preference: 60 Cost: 0
NextHop: 10.0.12.2 Neighbour: 0.0.0.0
State: Invalid Adv Relied Age: 00h27m53s
Tag: 0 Priority: medium
Label: NULL QoSInfo: 0x0
IndirectID: 0x80000001
RelayNextHop: 0.0.0.0 Interface: GigabitEthernet0/0/1
TunnelID: 0x0 Flags: R
Destination: 0.0.0.0/0
Protocol: Static Process ID: 0
Preference: 100 Cost: 0
NextHop: 10.0.13.2 Neighbour: 0.0.0.0
State: Active Adv Relied Age: 00h27m32s
Tag: 0 Priority: medium
Label: NULL QoSInfo: 0x0
IndirectID: 0x80000002
RelayNextHop: 0.0.0.0 Interface: GigabitEthernet0/0/2
TunnelID: 0x0 Flags: RD
BFD与OSPF联动
典型配置1
拓扑如图所示：
场景：两台路由器通过交换机互联，并将各自的接口运行于OSPF区域0，由于不是接口直接相连，若其中一台的接口Down，另一台不会立即感知，需要等待4倍的Hello时间来删除邻居，在这段时间内，数据转发都会处于非正常状态。在这种场景下，可以通过BFD检测来加快OSPF的收敛速度。
目标：通过BFD检测来加快OSPF的收敛速度。
配置步骤：
IP编址基本配置
OSPF配置
BFD会话配置
配置验证
1.IP编址基本配置
[R1]interface LoopBack 0
[R1-LoopBack0]ip add 10.0.1.1 32
[R1-LoopBack0]q
[R1]interface GigabitEthernet 0/0/1
[R1-GigabitEthernet0/0/1]ip add 10.1.12.1 24
[R1-GigabitEthernet0/0/1]q
[R2]interface LoopBack 0
[R2-LoopBack0]ip add 10.0.2.2 32
[R2-LoopBack0]q
[R2]interface GigabitEthernet 0/0/1
[R2-GigabitEthernet0/0/1]ip add 10.1.12.2 24
[R2-GigabitEthernet0/0/1]q
2.OSPF配置
[R1]ospf 1 router-id 10.0.1.1
[R1-ospf-1]area 0
[R1-ospf-1-area-0.0.0.0]network 10.0.1.1 0.0.0.0
[R1-ospf-1-area-0.0.0.0]network 10.1.12.0 0.0.0.255
[R1-ospf-1-area-0.0.0.0]q
[R1-ospf-1]q
[R2]ospf 1 router-id 10.0.2.2
[R2-ospf-1]area 0
[R2-ospf-1-area-0.0.0.0]network 10.0.2.2 0.0.0.0
[R2-ospf-1-area-0.0.0.0]network 10.1.12.0 0.0.0.255
[R2-ospf-1-area-0.0.0.0]q
[R2-ospf-1]q
3.BFD会话配置
#配置BFD会话
[R1]bfd //全局开启BFD
[R1-bfd]q
[R1]ospf 1
[R1-ospf-1]bfd all-interfaces enable //OSPF进程下使能BFD联动
[R1-ospf-1]q
[R2]bfd
[R2-bfd]q
[R2]ospf 1
[R2-ospf-1]bfd all-interfaces enable
[R2-ospf-1]q
#查看BFD session状态
--------------------------------------------------------------------------------
Local Remote PeerIpAddr State Type InterfaceName
--------------------------------------------------------------------------------
8192 8192 10.1.12.2 Up D_IP_IF GigabitEthernet0/0/1
--------------------------------------------------------------------------------
Total UP/DOWN Session Number : 1/0
--------------------------------------------------------------------------------
Local Remote PeerIpAddr State Type InterfaceName
--------------------------------------------------------------------------------
8192 8192 10.1.12.1 Up D_IP_IF GigabitEthernet0/0/1
--------------------------------------------------------------------------------
Total UP/DOWN Session Number : 1/0
4.配置验证
#在R1上开启debug，观察debug日志。
Dec 12 2024 00:22:47+00:00 R1 %%01BFD/4/STACHG_TODWN(l)[2]:BFD session changed to Down. (SlotNumber=0, Discriminator=8192, Diagnostic=DetectDown, Applications=OSPF, ProcessPST=False, BindInterfaceName=GigabitEthernet0/0/1, InterfacePhysicalState=Up, InterfaceProtocolState=Up)
Dec 12 2024 00:22:47+00:00 R1 %%01OSPF/3/NBR_CHG_DOWN(l)[3]:Neighbor event:neighbor state changed to Down. (ProcessId=1, NeighborAddress=10.1.12.2, NeighborEvent=KillNbr, NeighborPreviousState=Init, NeighborCurrentState=Down)
Dec 12 2024 00:22:47+00:00 R1 %%01OSPF/3/NBR_DOWN_REASON(l)[4]:Neighbor state leaves full or changed to Down. (ProcessId=1, NeighborRouterId=10.0.2.2, NeighborAreaId=0, NeighborInterface=GigabitEthernet0/0/1, NeighborDownImmediate reason=Neighbor Down Due to Kill Neighbor, NeighborDownPrimeReason=BFD Session Down, NeighborChangeTime=2024-12-12 00:22:47)
#在R2上shutdown端口，模拟链路故障。
[R2]interface GigabitEthernet 0/0/1
[R2-GigabitEthernet0/0/1]shutdown
BFD与VRRP联动
典型配置1
拓扑图如下
场景
R1通过两台交换机S1、S2和R2、R3互连，R2和R3运行VRRP作为局域网内R4和R5的网关，R2工作在VRRP MASTER模式，R3工作在BACKUP模式。为了避免R2的非直连上行链路Down后，上行流量依旧从R2转发形成路由黑洞的问题，配置BFD联动VRRP，当R1和R2互联接口Down掉，立即降低R2的VRRP优先级，由R3作为MASTER转发上行流量。
配置步骤：
1.基本IP编址
2.OSPF与静态路由配置
3.VRRP配置
4.配置BFD联动
5.测试
1.基本IP编址
[R1]interface LoopBack 0
[R1-LoopBack0]ip add 10.0.1.1 24
[R1-LoopBack0]q
[R1]interface GigabitEthernet 0/0/1
[R1-GigabitEthernet0/0/1]ip add 10.0.12.1 24
[R1-GigabitEthernet0/0/1]q
[R1]interface GigabitEthernet 0/0/2
[R1-GigabitEthernet0/0/2]ip add 10.0.13.1 24
[R1-GigabitEthernet0/0/2]q
[R2]interface LoopBack 0
[R2-LoopBack0]ip add 10.0.2.2 24
[R2-LoopBack0]q
[R2]interface GigabitEthernet 0/0/1
[R2-GigabitEthernet0/0/1]ip add 10.0.12.2 24
[R2-GigabitEthernet0/0/1]q
[R2]interface GigabitEthernet 0/0/0
[R2-GigabitEthernet0/0/0]ip add 192.168.45.2 24
[R2-GigabitEthernet0/0/0]q
[R3]interface LoopBack 0
[R3-LoopBack0]ip add 10.0.3.3 24
[R3-LoopBack0]q
[R3]interface GigabitEthernet 0/0/2
[R3-GigabitEthernet0/0/2]ip add 10.0.13.2 24
[R3-GigabitEthernet0/0/2]q
[R3]interface GigabitEthernet 0/0/0
[R3-GigabitEthernet0/0/0]ip add 192.168.45.3 24
[R3-GigabitEthernet0/0/0]q
[R4]interface GigabitEthernet 0/0/0
[R4-GigabitEthernet0/0/0]ip add 192.168.45.4 24
[R4-GigabitEthernet0/0/0]q
[R5]interface GigabitEthernet 0/0/0
[R5-GigabitEthernet0/0/0]ip add 192.168.45.5 24
[R5-GigabitEthernet0/0/0]q
[~SW1]vlan 12
[*SW1-vlan12]q
[*SW1]interface GE 1/0/1
[*SW1-GE1/0/1]port link-type access
[*SW1-GE1/0/1]port default vlan 12
[*SW1-GE1/0/1]q
[*SW1]interface GE 1/0/2
[*SW1-GE1/0/2]p l a
[*SW1-GE1/0/2]p d v 12
[*SW1-GE1/0/2]q
[*SW1]comm
[~SW1]
[~SW2]vlan 13
[*SW2-vlan13]q
[*SW2]interface GE 1/0/1
[*SW2-GE1/0/1]port link-type access
[*SW2-GE1/0/1]port default vlan 13
[*SW2-GE1/0/1]q
[*SW2]interface GE 1/0/3
[*SW2-GE1/0/3]p l a
[*SW2-GE1/0/3]p d v 13
[*SW2-GE1/0/3]q
[*SW2]comm
[~SW2]
2.OSPF与静态路由配置
[R1]ospf 1
[R1-ospf-1]area 0
[R1-ospf-1-area-0.0.0.0]network 10.0.1.0 0.0.0.255
[R1-ospf-1-area-0.0.0.0]network 10.0.12.0 0.0.0.255
[R1-ospf-1-area-0.0.0.0]network 10.0.13.0 0.0.0.255
[R1-ospf-1-area-0.0.0.0]q
[R1-ospf-1]q
[R2]ospf 1
[R2-ospf-1]area 0
[R2-ospf-1-area-0.0.0.0]network 10.0.2.0 0.0.0.255
[R2-ospf-1-area-0.0.0.0]network 10.0.12.0 0.0.0.255
[R2-ospf-1-area-0.0.0.0]network 192.168.45.0 0.0.0.255
[R2-ospf-1-area-0.0.0.0]q
[R2-ospf-1]silent-interface GigabitEthernet 0/0/0 //配置静默接口，该接口只宣告网段不建立邻居
[R3]ospf 1
[R3-ospf-1]area 0
[R3-ospf-1-area-0.0.0.0]network 10.0.3.0 0.0.0.255
[R3-ospf-1-area-0.0.0.0]network 10.0.13.0 0.0.0.255
[R3-ospf-1-area-0.0.0.0]network 192.168.45.0 0.0.0.255
[R3-ospf-1-area-0.0.0.0]q
[R3-ospf-1]silent-interface GigabitEthernet 0/0/0 //配置静默接口，该接口只宣告网段不建立邻居
#修改接口开销，使下行流量的选路以R2为主。
[R1]interface GigabitEthernet 0/0/1
[R1-GigabitEthernet0/0/1]ospf cost 90
[R1-GigabitEthernet0/0/1]q
[R1]interface GigabitEthernet 0/0/2
[R1-GigabitEthernet0/0/2]ospf cost 100
[R1-GigabitEthernet0/0/2]q
[R2]interface GigabitEthernet 0/0/1
[R2-GigabitEthernet0/0/1]ospf cost 90
[R2-GigabitEthernet0/0/1]q
[R3]interface GigabitEthernet 0/0/2
[R3-GigabitEthernet0/0/2]ospf cost 100
[R3-GigabitEthernet0/0/2]q
3.VRRP配置
#在R2、R3的下行接口配置VRRP。
[R2]interface GigabitEthernet 0/0/0
[R2-GigabitEthernet0/0/0]vrrp vrid 45 virtual-ip 192.168.45.1
[R2-GigabitEthernet0/0/0]vrrp vrid 45 priority 150 //华为设备默认优先级为100
[R2-GigabitEthernet0/0/0]q
[R3]interface GigabitEthernet 0/0/0
[R3-GigabitEthernet0/0/0]vrrp vrid 45 virtual-ip 192.168.45.1
[R3-GigabitEthernet0/0/0]q
#在R4和R5上配置默认路由指向VRRP地址
[R4]ip route-static 0.0.0.0 0 192.168.45.1
[R5]ip route-static 0.0.0.0 0 192.168.45.1
4.配置BFD联动
#在R1和R2上启用BFD，配置联动VRRP，如果BFD检测失效，立即降低优先级。
[R1]bfd
[R1-bfd]q
[R1]bfd 1 bind peer-ip 192.168.45.2 source-ip 10.0.12.1 auto
[R1-bfd-session-1]commit
[R1-bfd-session-1]q
[R2]bfd
[R2-bfd]q
[R2]bfd 1 bind peer-ip 10.0.12.1 source-ip 192.168.45.2 auto
[R2-bfd-session-1]com
[R2-bfd-session-1]q
[R2]interface GigabitEthernet 0/0/0
[R2-GigabitEthernet0/0/0]vrrp vrid 45 track bfd-session session-name 1 reduced 60 //检测到BFD失效时，降低接口VRRP优先级
5.测试
#当前VRRP状态
[R2]display vrrp
GigabitEthernet0/0/0 | Virtual Router 45
State : Master //主用模式
Virtual IP : 192.168.45.1
Master IP : 192.168.45.2
PriorityRun : 150 //当前运行优先级150
PriorityConfig : 150
MasterPriority : 150
Preempt : YES Delay Time : 0 s
TimerRun : 1 s
TimerConfig : 1 s
Auth type : NONE
Virtual MAC : 0000-5e00-012d
Check TTL : YES
Config type : normal-vrrp
Backup-forward : disabled
Track BFD : 1 Priority reduced : 60 //BFD失效时降低优先级
BFD-session state : UP
Create time : 2024-12-26 00:26:22
Last change time : 2024-12-26 00:26:25
#模拟BFD失效
[R4]ping -c 100 10.0.1.1
[R1]interface GigabitEthernet 0/0/1
[R1-GigabitEthernet0/0/1]shutdown
#在R4上查看ping的结果
PING 10.0.1.1: 56 data bytes, press CTRL_C to break
Reply from 10.0.1.1: bytes=56 Sequence=1 ttl=254 time=3 ms
Reply from 10.0.1.1: bytes=56 Sequence=2 ttl=254 time=4 ms
Reply from 10.0.1.1: bytes=56 Sequence=3 ttl=254 time=4 ms
Reply from 10.0.1.1: bytes=56 Sequence=6 ttl=254 time=3 ms
Reply from 10.0.1.1: bytes=56 Sequence=37 ttl=254 time=6 ms
Request time out
Request time out
Reply from 10.0.1.1: bytes=56 Sequence=40 ttl=254 time=4 ms
Reply from 10.0.1.1: bytes=56 Sequence=41 ttl=254 time=2 ms
Reply from 10.0.1.1: bytes=56 Sequence=42 ttl=254 time=3 ms
GigabitEthernet0/0/0 | Virtual Router 45
State : Backup
Virtual IP : 192.168.45.1
Master IP : 192.168.45.3
PriorityRun : 90
PriorityConfig : 150
MasterPriority : 100
Preempt : YES Delay Time : 0 s
TimerRun : 1 s
TimerConfig : 1 s
Auth type : NONE
Virtual MAC : 0000-5e00-012d
Check TTL : YES
Config type : normal-vrrp
Backup-forward : disabled
Track BFD : 1 Priority reduced : 60
BFD-session state : DOWN
Create time : 2024-12-26 00:26:22
Last change time : 2024-12-26 01:24:37