一、Isis路由引入概念
ISIS路由引入是链路状态协议中的关键机制，主要用于将外部路由信息（如静态路由、直连路由或其他动态协议的路由）导入ISIS域内进行分发。其核心特点包括：
多协议整合性：
支持将不同来源的路由（如OSPF、BGP等）通过策略控制注入ISIS域，实现异构网络环境下的全域路由可达。
策略化控制:
支持通过路由过滤（ACL/前缀列表）筛选待引入路由
可自定义度量值（Metric）设置，与ISIS内部路径计算机制协同
层级化实现:
在不同ISIS层级（Level-1/Level-2）间执行路由引入时，需配合路由泄露（Route Leaking）策略，避免次优路径问题。
与流量工程协同:
在多路径场景中，通过精细化的路由引入策略可优化流量分布，例如在域间路由场景下实现不相交路径选择。
二、应用场景
ISIS属于链路状态路由协议，通常用于大型网络，尤其是在ISP中比较常见。路由引入是指将其他路由协议的路由信息导入到ISIS中，或者在不同ISIS域之间进行路由的重新分发。
三、综合实验
1、实验拓扑
2、配置命令
<Huawei>sys
[Huawei]un in e
[Huawei]sysname r1
[r1]interface g0/0/0
[r1-GigabitEthernet0/0/0]ip address 12.1.1.1 24
[r1-GigabitEthernet0/0/0]quit
[r1]interface LoopBack 0
[r1-LoopBack0]ip address 1.1.1.1 32
[r1-LoopBack0]quit
[r1]isis
[r1-isis-1]network-e
[r1-isis-1]network-entity 49.0123.0000.0000.0001.00
[r1-isis-1]is-level level-2
[r1-isis-1]cost-style wide
[r1-isis-1]quit
[r1]inter
[r1]interface g0/0/0
[r1-GigabitEthernet0/0/0]isis enable
[r1-GigabitEthernet0/0/0]quit
[r1]inter
[r1]interface loop
[r1]interface LoopBack 0
[r1-LoopBack0]isis enable
[r1-LoopBack0]quit
#配置环回口
[r1]interface LoopBack 100
[r1-LoopBack100]ip address 100.100.100.100 32
[r1-LoopBack100]quit
[r1]isis
[r1-isis-1]import-route direct
[r1-isis-1]quit
<Huawei>sys
[Huawei]un in e
[Huawei]sysname r2
[r2]inter
[r2]interface g0/0/1
[r2-GigabitEthernet0/0/1]ip address 12.1.1.2 24
[r2-GigabitEthernet0/0/1]quit
[r2]interface g0/0/0
[r2-GigabitEthernet0/0/0]ip address 23.1.1.2 24
[r2-GigabitEthernet0/0/0]quit
[r2]interface LoopBack 0
[r2-LoopBack0]ip address 2.2.2.2 32
[r2-LoopBack0]quit
[r2]isis
[r2-isis-1]network-entity 49.0123.0000.0000.0002.00
[r2-isis-1]is-level level-2
[r2-isis-1]cost-style wide
[r2-isis-1]quit
[r2]inter
[r2]interface g0/0/0
[r2-GigabitEthernet0/0/0]isis enable
[r2-GigabitEthernet0/0/0]quit
[r2]inter
[r2]interface g0/0/1
[r2-GigabitEthernet0/0/1]isis enable
[r2-GigabitEthernet0/0/1]quit
[r2]interface LoopBack 0
[r2-LoopBack0]isis enable
[r2-LoopBack0]quit
<r2>
<Huawei>sys
[Huawei]un in e
[Huawei]sysname r3
[r3]inter
[r3]interface g0/0/1
[r3-GigabitEthernet0/0/1]ip address 23.1.1.3 24
[r3-GigabitEthernet0/0/1]quit
[r3]interface g0/0/0
[r3-GigabitEthernet0/0/0]ip address 34.1.1.3 24
[r3-GigabitEthernet0/0/0]quit
[r3]interface LoopBack 0
[r3-LoopBack0]ip address 3.3.3.3 32
[r3-LoopBack0]quit
[r3]isis
[r3-isis-1]network
[r3-isis-1]network-entity 49.0123.0000.0000.0003.00
[r3-isis-1]is-level level-2
[r3-isis-1]cost-style wide
Info: Cost style changed, Resetting ISIS...
[r3-isis-1]quit
[r3]interface g0/0/1
[r3-GigabitEthernet0/0/1]isis enable
[r3-GigabitEthernet0/0/1]quit
[r3]interface g0/0/0
[r3-GigabitEthernet0/0/0]isis enable
[r3-GigabitEthernet0/0/0]quit
[r3]interface LoopBack 0
[r3-LoopBack0]isis enable
[r3-LoopBack0]quit
[r3]display ip routing-table
[r3]display isis route 8.8.8.0 verbose
<Huawei>sys
[Huawei]un in e
[Huawei]sysname r4
[r4]interface g0/0/1
[r4-GigabitEthernet0/0/1]ip address 34.1.1.4 24
[r4-GigabitEthernet0/0/1]quit
[r4]interface LoopBack 0
[r4-LoopBack0]ip address 4.4.4.4 24
[r4-LoopBack0]quit
[r4]
[r4]isis
[r4-isis-1]network-entity 49.0004.0000.0000.0004.00
[r4-isis-1]is-level level-2
[r4-isis-1]cost-style wide
[r4-isis-1]quit
[r4]inter
[r4]interface g0/0/1
[r4-GigabitEthernet0/0/1]isis enable
[r4-GigabitEthernet0/0/1]quit
[r4]interface LoopBack 0
[r4-LoopBack0]isis enable
[r4-LoopBack0]quit
[r4]display ip routing-table 配置完成后在R3上查看路由表，查看到直连路由已经引入IS-IS
<r3>dis ip routing-table
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 17 Routes : 17
Destination/Mask Proto Pre Cost Flags NextHop Interface
1.1.1.1/32 ISIS-L2 15 20 D 23.1.1.2 GigabitEthernet0/0/1
2.2.2.2/32 ISIS-L2 15 10 D 23.1.1.2 GigabitEthernet0/0/1
3.3.3.3/32 Direct 0 0 D 127.0.0.1 LoopBack0
4.4.4.0/24 ISIS-L2 15 10 D 34.1.1.4 GigabitEthernet0/0/0
8.8.8.0/24 ISIS-L2 15 50 D 23.1.1.2 GigabitEthernet0/0/1
12.1.1.0/24 ISIS-L2 15 20 D 23.1.1.2 GigabitEthernet0/0/1
23.1.1.0/24 Direct 0 0 D 23.1.1.3 GigabitEthernet0/0/1
23.1.1.3/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/1
23.1.1.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/1
34.1.1.0/24 Direct 0 0 D 34.1.1.3 GigabitEthernet0/0/0
34.1.1.3/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
34.1.1.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
100.100.100.100/32 ISIS-L2 15 20 D 23.1.1.2 GigabitEthernet0/0/1
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
127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0在R1上配置一条静态路由，将其引入IS-IS
[r1]ip route-static 8.8.8.0 24 NULL 0
[r1]isis
[r1-isis-1]import-route static cost 30 tag 888
[r1-isis-1]q查看IS-IS路由表
<r3>display isis route 8.8.8.0 verbose
Route information for ISIS(1)
-----------------------------
ISIS(1) Level-2 Forwarding Table
--------------------------------
IPV4 Dest : 8.8.8.0/24 Int. Cost : 50 Ext. Cost : NULL
Admin Tag : 888 Src Count : 1 Flags : A/-/-/-
Priority : Low
NextHop : Interface : ExitIndex :
23.1.1.2 GE0/0/1 0x00000004
Flags: D-Direct, A-Added to URT, L-Advertised in LSPs, S-IGP Shortcut,
U-Up/Down Bit Set在R4上查看IS-IS路由表
<r4>dis ip routing-table
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 17 Routes : 17
Destination/Mask Proto Pre Cost Flags NextHop Interface
1.1.1.1/32 ISIS-L2 15 30 D 34.1.1.3 GigabitEthernet0/0/1
2.2.2.2/32 ISIS-L2 15 20 D 34.1.1.3 GigabitEthernet0/0/1
3.3.3.3/32 ISIS-L2 15 10 D 34.1.1.3 GigabitEthernet0/0/1
4.4.4.0/24 Direct 0 0 D 4.4.4.4 LoopBack0
4.4.4.4/32 Direct 0 0 D 127.0.0.1 LoopBack0
4.4.4.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
8.8.8.0/24 ISIS-L2 15 60 D 34.1.1.3 GigabitEthernet0/0/1
12.1.1.0/24 ISIS-L2 15 30 D 34.1.1.3 GigabitEthernet0/0/1
23.1.1.0/24 ISIS-L2 15 20 D 34.1.1.3 GigabitEthernet0/0/1
34.1.1.0/24 Direct 0 0 D 34.1.1.4 GigabitEthernet0/0/1
34.1.1.4/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/1
34.1.1.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/1
100.100.100.100/32 ISIS-L2 15 30 D 34.1.1.3 GigabitEthernet0/0/1
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
127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0四、总结
通过灵活控制外部路由的传播范围与优先级，满足复杂网络拓扑中的流量工程需求。典型应用场景包括多自治系统互联、跨协议域组播分发等