配置IS-IS快速收敛配置实例
组网需求
如下图所示。
路由器RouterA和RouterB之间运行IS-IS协议。
路由器RouterA和RouterB同属于区域10，都是Level-2路由器。
配置IS-IS快速收敛示例
配置思路
采用如下思路配置IS-IS快速收敛特性：
在各路由器上使能IS-IS基本功能。
在RouterA和RouterB上使能BFD检测机制。
在RouterA和RouterB上关闭hello报文填充。
在RouterA和RouterB上配置快速收敛时间参数。
数据准备
为完成此配置例，需准备如下的数据：
三台路由器的级别和所属区域号。
快速收敛时间参数值。
配置步骤
步骤 1 配置各路由器接口的IP地址（略）
步骤 2 配置IS-IS基本功能
# 配置RouterA。 [RouterA] isis 1 [RouterA-isis-1] is-level level-2 [RouterA-isis-1] network-entity 10.0000.0000.0001.00 [RouterA-isis-1] quit [RouterA] interface GigabitEthernet 1/0/0 [RouterA- GigabitEthernet1/0/0] isis enable 1 [RouterA- GigabitEthernet1/0/0] quit # 配置RouterB。 [RouterB] isis 1 [RouterB-isis-1] is-level level-2 [RouterB-isis-1] network-entity 10.0000.0000.0002.00 [RouterB-isis-1] quit [RouterB] interface GigabitEthernet 1/0/0 [RouterB-GigabitEthernet1/0/0] isis enable 1 [RouterB-GigabitEthernet1/0/0] quit # 在RouterA上查看邻居状态和路由计算时间。 在RouterB的GE1/0/0端口上执行命令shutdown，模拟链路down掉。 [RouterB] interface GigabitEthernet 1/0/0 [RouterB-GigabitEthernet1/0/0] shutdown
在RouterA上查看邻居信息。
<RouterA> debugging isis spf-summary
<RouterA> terminal debugging
<RouterA> terminal monitor
<RouterA> display isis peer
Peer information for ISIS(1)
----------------------------
System Id Interface Circuit Id State HoldTime Type PRI
0000.0000.0002 Ge1/0/0 0000.0000.0002.01 Up 7s L2 64
由于在RouterB的GE口上执行shutdown命令，系统会维持holdtime时间，并不马上宣告邻居失效，直到holdtime时间超时后才删除邻居，这时会激发路由计算。
*0.11042110 Quidway ISIS/7/ISIS:
Prc job completed at Sec = 11019, MSec = 750.
*0.11042110 Quidway ISIS/7/ISIS:
Signal SPF at Sec = 11042, MSec = 110.
*0.11052110 Quidway ISIS/7/ISIS:
Signal SPF at Sec = 11042, MSec = 110.
*0.11052110 Quidway ISIS/7/ISIS:
ISpf starts at Sec = 11052, MSec = 110.ISIS-1-SPF-STATS: RT Calculation: Elapsed time: 0 Milliseconds
*0.11052110 Quidway ISIS/7/ISIS:
ISIS-1-SPF-PRC: Received L2 System Change Event for 0000.0000.0002.00, Change =2
*0.11052110 Quidway ISIS/7/ISIS:
ISIS-1-SPF-PRC: Received L2 System Change Event for 0000.0000.0002.01, Change =2
*0.11052110 Quidway ISIS/7/ISIS:
ISIS-1-DEC-PRC: Igorning pseudo-node system change information from the ISPF module.
*0.11052110 Quidway ISIS/7/ISIS:
*0.11052110 Quidway ISIS/7/ISIS:
ISpf ends(and prc starts) at Sec = 11052, MSec = 110.
*0.11052110 Quidway ISIS/7/ISIS:
Prc job starts to run at Sec = 11052, MSec = 110.ISIS-1-SPF-PRC: Processing L2
LSPs of System :0000.0000.0002, Change Type = 2
在holdtime时间内，通过GE1/0/0接口的路由将被丢弃，导致报文不能正确送达。这时需要使能BFD特性和配置快速收敛时间参数，以保证在网络变化时，路由器可以迅速感知拓扑变化并重新计算路由。
步骤 3 配置BFD特性
# 配置RouterA。 [RouterA] bfd [RouterA-bfd] quit [RouterA] interface GigabitEthernet 1/0/0 [RouterA-GigabitEthernet1/0/0] bfd [RouterA-GigabitEthernet1/0/0] quit [RouterA] bfd atob bind peer-ip 10.1.1.2 interface GigabitEthernet 1/0/0 [RouterA-bfd-session-atob] discriminator local 1 [RouterA-bfd-session-atob] discriminator remote 2 [RouterA-bfd-session-atob] commit [RouterA-bfd-session-atob] quit [RouterA] interface GigabitEthernet 1/0/0 [RouterA-GigabitEthernet1/0/0] isis fast-sense [RouterA-GigabitEthernet1/0/0] quit # 配置RouterB。 [RouterB] bfd [RouterB-bfd] quit [RouterB] interface GigabitEthernet 1/0/0 [RouterB-GigabitEthernet1/0/0] bfd [RouterB-GigabitEthernet1/0/0] quit [RouterB] bfd atob bind peer-ip 10.1.1.1 interface GigabitEthernet 1/0/0 [RouterB-bfd-session-atob] discriminator local 2 [RouterB-bfd-session-atob] discriminator remote 1 [RouterB-bfd-session-atob] commit [RouterB-bfd-session-atob] quit [RouterB] interface GigabitEthernet 1/0/0 [RouterB-GigabitEthernet1/0/0] isis fast-sense [RouterB-GigabitEthernet1/0/0] quit
步骤 4 关闭hello报文填充
# 配置RouterA。 [RouterA] interface GigabitEthernet 1/0/0 [RouterA-GigabitEthernet1/0/0] isis small-hello [RouterA-GigabitEthernet1/0/0] quit # 配置RouterB [RouterB] interface GigabitEthernet 1/0/0 [RouterB-GigabitEthernet1/0/0] isis small-hello [RouterB-GigabitEthernet1/0/0] quit
在邻接关系的建立过程中，IS-IS需要检查链路两端的MTU大小是否一致。缺省情况下，IS-IS协议将Hello报文填充至MTU大小。可以通过该命令简化Hello报文的收发操作，减小对网络带宽的浪费。
步骤 5 配置快速收敛时间参数
# 配置RouterA。 [RouterA] isis [RouterA-isis-1] timer spf 1 50 100 [RouterA-isis-1] timer lsp-generation 1 1 120 # 配置RouterB。 [RouterB] isis [RouterB-isis-1] timer spf 1 50 100 [RouterB-isis-1] timer lsp-generation 1 1 120
说明
spf默认值：10s、100ms、5s
lsp-generation默认值：5s、50ms、5s
步骤 6 检查配置结果
# 在RouterB的GE1/0/0端口上执行命令shutdown，模拟链路down掉。
[RouterB] interface GigabitEthernet 1/0/0
[RouterB-GigabitEthernet1/0/0] shutdown
# 在RouterA上查看路由计算时间。
<RouterA> debugging isis spf-summary
<RouterA> terminal debugging
<RouterA> terminal monitor
%Sep 26 12:10:29 2006 Quidway BFD/5/BFD:IO(6) BFD Session(Discr:1) FSM Change To Down(Detect)
%Sep 26 12:10:29 2006 Quidway RM/4/RMLOG:ISIS-FastSense: Deleting Neighbour by IP Address 10.1.1.2 On GigabitEthernet1/0/0 *0.9978760 Quidway ISIS/7/ISIS:
Prc job completed at Sec = 09919, MSec = 390.*0.9978760 Quidway ISIS/7/ISIS:
Signal SPF at Sec = 09978, MSec = 760.*0.9978870 Quidway ISIS/7/ISIS:
Signal SPF at Sec = 09978, MSec = 760.*0.9978870 Quidway ISIS/7/ISIS:
ISpf starts at Sec = 09978, MSec = 810.ISIS-1-SPF-STATS: RT Calculation: Elapsed time: 0 Milliseconds
*0.9978870 Quidway ISIS/7/ISIS:
ISIS-1-SPF-PRC: Received L2 System Change Event for 0000.0000.0002.00, Change =2*0.9978870 Quidway ISIS/7/ISIS:
ISIS-1-SPF-PRC: Received L2 System Change Event for 0000.0000.0002.01, Change =2*0.9978870 Quidway ISIS/7/ISIS:
ISIS-1-DEC-PRC: Igorning pseudo-node system change information from the ISPF module.*0.9978870 Quidway ISIS/7/ISIS:
*0.9978870 Quidway ISIS/7/ISIS:
ISpf ends(and prc starts) at Sec = 09978, MSec = 810.*0.9978870 Quidway ISIS/7/ISIS:
Prc job starts to run at Sec = 09978, MSec = 810.ISIS-1-SPF-PRC: Processing L2
LSPs of System :0000.0000.0002, Change Type = 2
当BFD感知链路down掉时，立刻删除邻居，激发路由计算，使网络迅速收敛。
