學習回顧—IS-IS路由協定(0x32)-IS-IS與靜态BFD關聯的配置示例

本示例的基本拓撲結構如圖所示，現網中有3台路由器通過IS-IS協定實作路由互通，且Router-A和Router-B之間通過一台二層交換機及實作互聯。現要求當Router-A與Router-B之間出現鍊路故障時，能快速檢測到。

由于本執行個體中Router-A和Router-C中間隔了一個Router-B，是以不能建立IS-IS鄰居，不能通過IS-IS與BFD的關聯檢測Router-A到Router-C之間的多跳鍊路(因為IS-IS還隻能建立單跳鄰居關系)，隻能正在Router-A和Router-B之間檢測單跳鍊路。

1) 配置各路由器的接口IP位址

【Router-A上的配置】

interface GigabitEthernet1/0/0

ip address 10.1.1.1 255.255.255.0

#

【Router-B上的配置】

interface GigabitEthernet1/0/0

ip address 10.1.1.2 255.255.255.0

#

interface GigabitEthernet2/0/0

ip address 10.2.1.1 255.255.255.0

#

【Router-C上的配置】

interface GigabitEthernet1/0/0

ip address 10.2.1.2 255.255.255.0

#

2) 配置各路由器的IS-IS基本功能

【Router-A上的配置】

isis 1

is-level level-2

network-entity aa.1111.1111.1111.00

#

interface GigabitEthernet1/0/0

ip address 10.1.1.1 255.255.255.0

isis enable 1

#

【Router-B上的配置】

isis 1

is-level level-2

network-entity aa.2222.2222.2222.00

#

interface GigabitEthernet1/0/0

ip address 10.1.1.2 255.255.255.0

isis enable 1

#

interface GigabitEthernet2/0/0

ip address 10.2.1.1 255.255.255.0

isis enable 1

【Router-C上的配置】

isis 1

is-level level-2

network-entity aa.3333.3333.3333.00

#

interface GigabitEthernet1/0/0

ip address 10.2.1.2 255.255.255.0

isis enable 1

【在RouterA上執行display isis peer指令，即可以看到Router-A和Router-B建立鄰居關系】

<Router-A>display isis peer

Peer information for ISIS(1)

System Id Interface Circuit Id State HoldTime Type PRI

-------------------------------------------------------------------------------

2222.2222.2222 GE1/0/0 1111.1111.1111.01 Up 26s L2 64

Total Peer(s): 1

<Router-A>

【在RouterA上執行display isis route指令，即可以看到Router-A和Router-B建立鄰居關系】

<Router-A>display isis route

Route information for ISIS(1)

-----------------------------

ISIS(1) Level-2 Forwarding Table

--------------------------------

IPV4 Destination IntCost ExtCost ExitInterface NextHop Flags

---------------------------------------------------------------------------

10.1.1.0/24 10 NULL GE1/0/0 Direct D/-/L/-

10.2.1.0/24 20 NULL GE1/0/0 10.1.1.2 A/-/-/-

Flags: D-Direct, A-Added to URT, L-Advertised in LSPs, S-IGP Shortcut,

U-Up/Down Bit Set

<Router-A>

3) 在Router-A和Router-B上分别配置IS-IS與靜态BFD關聯，包括建立BFD會話

【Router-A上的配置】

bfd

#

bfd atob bind peer-ip 10.1.1.2 interface GigabitEthernet1/0/0

discriminator local 1

discriminator remote 2

commit

#

interface GigabitEthernet1/0/0

ip address 10.1.1.1 255.255.255.0

isis enable 1

isis bfd static

【Router-B上的配置】

bfd

#

#

bfd btoa bind peer-ip 10.1.1.1 interface GigabitEthernet1/0/0

discriminator local 2

discriminator remote 1

commit

#

interface GigabitEthernet1/0/0

ip address 10.1.1.2 255.255.255.0

isis enable 1

isis bfd static

#

4) 配置驗證

l 以上配置後後，通過在Router-A或Router-B上執行display bfd session指令可以看到它們之間的BFD會話的狀态為Up。

<Router-A>display bfd session all

---------------------------------------------------------------------------

Local Remote PeerIpAddr State Type InterfaceName

---------------------------------------------------------------------------

1 2 10.1.1.2 Up S_IP_IF GigabitEthernet1/0/0

---------------------------------------------------------------------------

Total UP/DOWN Session Number : 1/0

<Router-A>

在Router-A上打開終端顯示資訊中心發送的日志資訊功能。

<Router-A>terminal logging

Info: Current terminal logging is on.

<Router-A>terminal monitor

Info: Current terminal monitor is on.

<Router-A>

l 對Router-B的G1/0/0接口執行shutdown指令，模拟鍊路故障。

<Router-A>

May 15 2023 13:08:27-08:00 Router-A %%01BFD/4/STACHG_TODWN(l)[1]:BFD session changed to Down. (SlotNumber=0, Discriminator=16777216, Diagnostic=DetectDown, Applications=None, ProcessPST=False, BindInterfaceName=GigabitEthernet1/0/0, InterfacePhysicalState=Up, InterfaceProtocolState=Up)

<Router-A>

May 15 2023 13:08:27-08:00 Router-A %%01ISIS/4/PEER_DOWN_BFDDOWN(l)[2]:ISIS 256 neighbor 2222.2222.2222 was Down on interface GE1/0/0 because the BFD node was down. The Hello packet was received at 13:05:43 last time; the maximum interval for sending Hello packets was 438763520; the local router sent 1980500224 Hello packets and received 419758080 packets; the type of the Hello packet was Lan Level-2.

<Router-A>

May 15 2023 13:08:27-08:00 Router-A %%01ISIS/4/ADJ_CHANGE_LEVEL(l)[3]:The neighbor of ISIS was changed. (IsisProcessId=256, Neighbor=2222.2222.2222, InterfaceName=GE1/0/0, CurrentState=up, ChangeType=L2_BFD_DOWN, Level=Level-2)

<Router-A>

May 15 2023 13:08:27-08:00 Router-A %%01ISIS/4/ADJ_CHANGE_LEVEL(l)[4]:The neighbor of ISIS was changed. (IsisProcessId=256, Neighbor=2222.2222.2222, InterfaceName=GE1/0/0, CurrentState=down, ChangeType=L2_HOLDTIMER_EXPIRED, Level=Level-2)

<Router-A>

l 再在Router-A上執行display isis route或display isis peer指令，沒有顯示任何資訊，表明Router-A與Router-B之間的IS-IS鄰居關系已經拆除。

<Router-A>display isis peer

<Router-A>