bfd动态该如何配置

如下图拓扑所示：

SW1 与 SW2 交换机采用静态链路聚合模式部署。

为避免由于链路感知延迟（如长距离链路，或链路中存在有源传输设备），导致可能出现的“黑洞”现象（一端链路接口UP，另一端链路接口Down），增加BFD功能。实现链路聚合快速毫秒级感知链路状态。

<SW1>

#

interface Bridge-Aggregation1

 link-aggregation bfd ipv4 source 1.1.1.1 destination 2.2.2.2

 bfd authentication-mode simple 1 plain 123 //可选，配置密钥123

#

interface Ten-GigabitEthernet1/0/1

 port link-mode bridge

 link-aggregation port-priority 4096

 port link-aggregation group 1

#

interface Ten-GigabitEthernet1/0/3

 port link-mode bridge

 port link-aggregation group 1

#

<SW2>

#

interface Bridge-Aggregation1

 link-aggregation bfd ipv4 source 2.2.2.2 destination 1.1.1.1

 bfd authentication-mode simple 1 plain 123 //可选，配置密钥123

#

interface Ten-GigabitEthernet1/0/1

 port link-mode bridge

 port link-aggregation group 1

#

interface Ten-GigabitEthernet1/0/3

 port link-mode bridge

 port link-aggregation group 1

#

当链路正常情况下：

<SW1> display link-aggregation verbose

……

Aggregate Interface: Bridge-Aggregation1

Aggregation Mode: Static

Loadsharing Type: Shar

Management VLANs: None

  Port             Status      Priority  Oper-Key

  XGE1/0/1(R)      S       4096     1        

  XGE1/0/3           S       32768   1

<SW1> display bfd session

 Total Session Num: 2     Up Session Num: 2     Init Mode: Active

 IPv4 session working in control packet mode:

 LD/RD          SourceAddr      DestAddr        State    Holdtime    Interface

 257/257        1.1.1.1         2.2.2.2         Up       1983ms      XGE1/0/1  

 258/258        1.1.1.1         2.2.2.2         Up       1703ms      XGE1/0/3 

<SW2>display link-aggregation verbose

……

Aggregate Interface: Bridge-Aggregation1

Aggregation Mode: Static

Loadsharing Type: Shar

Management VLANs: None

  Port             Status      Priority   Oper-Key

  XGE1/0/1(R)      S       32768    1        

  XGE1/0/3           S       32768    1

<SW2>display bfd session

 Total Session Num: 2     Up Session Num: 2     Init Mode: Active

 IPv4 session working in control packet mode:

 LD/RD          SourceAddr      DestAddr        State    Holdtime    Interface

 257/257        2.2.2.2         1.1.1.1         Up       2000ms      XGE1/0/1  

 258/258        2.2.2.2         1.1.1.1         Up       1966ms      XGE1/0/3 

若SW2本地XG1/0/1接口down后，及链路故障时：

<SW1>

%Jan 28 03:34:10:784 1980 sw1 BFD/5/BFD_CHANGE_FSM: Sess[1.1.1.1/2.2.2.2, LD/RD:259/259, Interface:XGE1/0/1, SessType:Ctrl, LinkType:INET], Ver:1, Sta: UP->DOWN, Diag: 1 (Control Detection Time Expired)   //SW1的bfd会话快速感知到会话down

*Jan 28 03:34:10:785 1980 sw1 LAGG/7/Event: Group 1 updated because of member port BFD session up/down.

*Jan 28 03:34:10:830 1980 sw1 LAGG/7/Event: Group 1 updated because of other reason.

%Jan 28 03:34:10:838 1980 sw1 LAGG/6/LAGG_INACTIVE_BFD: Member port XGE1/0/1 of aggregation group BAGG1 changed to the inactive state, because the BFD session state of the port is down.  //BFD模块通知链路聚合模块相关接口出现“异常”，需要将SW1本地对应链路接口置为Unselected状态。

%Jan 28 03:34:10:843 1980 sw1 IFNET/5/LINK_UPDOWN: Line protocol state on the interface Ten-GigabitEthernet1/0/1 changed to down.    //SW1本地XG1/0/1接口逻辑链路层快速被down掉。

<SW1>display link-aggregation verbose

……

Aggregate Interface: Bridge-Aggregation1

Aggregation Mode: Static

Loadsharing Type: Shar

Management VLANs: None

  Port                  Status  Priority Oper-Key

  XGE1/0/1         U          4096     1   

  XGE1/0/3(R)    S          32768    1

<sw1>display bfd session

 Total Session Num: 1     Up Session Num: 1     Init Mode: Active

 IPv4 session working in control packet mode:

 LD/RD          SourceAddr      DestAddr        State    Holdtime    Interface

 258/258        1.1.1.1         2.2.2.2         Up       1737ms      XGE1/0/3 

<SW2>display link-aggregation verbose

……

Aggregate Interface: Bridge-Aggregation1

Aggregation Mode: Static

Loadsharing Type: Shar

Management VLANs: None

  Port             Status  Priority Oper-Key

  XGE1/0/3(R)      S       32768    1    

<SW2>display bfd sesion

 Total Session Num: 1     Up Session Num: 1     Init Mode: Active

 IPv4 session working in control packet mode:

 LD/RD          SourceAddr      DestAddr        State    Holdtime    Interface

 258/258        2.2.2.2         1.1.1.1         Up       1899ms      XGE1/0/3