14.静态路由及静态 BFD

14.静态路由及静态 BFD | Evergreen Notes

静态路由及静态 BFD

实验需求

在SW1/SW2上完成静态路由的配置，使得SW1能够访问PC。
SW1与SW2中间的交换机为非可网管交换机。确保在非可网管交换机与SW2之间的链路发生故障、或者SW2发生故障的情况下，SW1能够感知并且将关于PC所在网段的静态路由从路由表中撤销。

SW1的配置如下

[SW1] vlan 12
[SW1-vlan12] quit
[SW1] interface gigabitEthernet 0/0/24
[SW1-GigabitEthernet0/0/24] port link-type trunk
[SW1-GigabitEthernet0/0/24] port trunk allow-pass vlan 12
[SW1] interface Vlanif 12
[SW1-vlanif12] ip address 10.1.12.1 24
[SW1] bfd #激活BFD
[SW1-bfd] quit
[SW1] bfd bfd12 bind peer-ip 10.1.12.2 #创建BFD会话bfd12，用于检测10.1.12.2
[SW1-bfd-session-bfd12] discriminator local 11 #对应SW2的remote 22

SW2的配置如下

完成上述配置后，SW1与SW2之间的BFD会话便会开始工作，彼此之间会进行BFD心跳报文的交互（如下图所示），当网络正常时，BFD会话的状态是UP的，在SW1上执行display bfd session all 命令，可以查看BFD会话：

现在来模拟网络发生故障的情况，将SW2的vlanif 12接口shutdown，以此来模拟SW1-SW2之间连接故障的情况（或者可以将非可网管交换机与SW2的连线掐断）。我们发现在SW2的vlanif 12接口被shutdown之后，SW1与SW2之间的BFD会话立即失效（状态变为Down），我们可以在SW1 上看到如下日志：

BFD会话的状态已经是Down了，而由于SW1去往192.168.10.0/24网段的静态路由是与该BFD会话绑定的，因此当这个BFD会话状态为Down时，静态路由将失效。此时，SW1的路由表立即发生了变化：

[SW2] vlan batch 10 12
[SW2] interface GigabitEthernet 0/0/1
[SW2-GigabitEthernet0/0/1] port link-type access #连接PC的接口配置为access类型
[SW2-GigabitEthernet0/0/1] port default vlan 10
[SW2] interface gigabitEthernet 0/0/24
[SW2-GigabitEthernet0/0/24] port link-type trunk
[SW2-GigabitEthernet0/0/24] port trunk allow-pass vlan 12
[SW2] interface Vlanif 10
[SW2-vlanif10] ip address 192.168.10.254 24
[SW2] interface Vlanif 12
[SW2-vlanif12] ip address 10.1.12.2 24
[SW2] bfd
[SW2-bfd] quit
[SW2] bfd bfd12 bind peer-ip 10.1.12.1
[SW2-bfd-session-bfd12] discriminator local 22
[SW2-bfd-session-bfd12] discriminator remote 11
[SW2-bfd-session-bfd12] commit

<S1>display bfd session all
--------------------------------------------------------------------------------
Local Remote     PeerIpAddr      State     Type        InterfaceName            
--------------------------------------------------------------------------------
 
11    22         10.1.12.2       Up        S_IP_PEER         -                  
--------------------------------------------------------------------------------
     Total UP/DOWN Session Number : 1/0

[SW1] display ip routing-table
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
 Destinations : 5 Routes : 5
Destination/Mask Proto Pre Cost Flags NextHop Interface
 192.168.10.0/24 Static 60 0 RD 10.1.12.2 Vlanif12
 10.1.12.0/24 Direct 0 0 D 10.1.12.1 Vlanif12
 10.1.12.1/32 Direct 0 0 D 127.0.0.1 Vlanif12

Apr 3 2016 00:34:21-08:00 SW1 %%01BFD/4/STACHG_TODWN(l)[3]:BFD session changed
to Down. (SlotNumber=0, Discriminator=11, Diagnostic=DetectDown, Applications=No
ne, ProcessPST=False, BindInterfaceName=None, InterfacePhysicalState=None, Inter
faceProtocolState=None)
查看SW1的BFD会话
<S1>display bfd session all
--------------------------------------------------------------------------------
Local Remote     PeerIpAddr      State     Type        InterfaceName            
--------------------------------------------------------------------------------
 
11    22         10.1.12.2       Down      S_IP_PEER         -                  
--------------------------------------------------------------------------------
     Total UP/DOWN Session Number : 0/1

<S1>display ip routing-table
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
         Destinations : 4        Routes : 4        
 
Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface
 
      10.1.12.0/24  Direct  0    0           D   10.1.12.1       Vlanif12
      10.1.12.1/32  Direct  0    0           D   127.0.0.1       Vlanif12
      127.0.0.0/8   Direct  0    0           D   127.0.0.1       InLoopBack0
      127.0.0.1/32  Direct  0    0           D   127.0.0.1       InLoopBack0