为什么需要路有泄漏

1. level2和level1的关系：level2可以学习到level 1中的具体路由信息，level 1无法得到level 2的具体路由，只能通过缺省路由访问
2. FIB（信息转发表），即数据转发，多条链路可达时由于路由负载，要通过随机的数据中的五元组hash，hash值决定数据放到哪些链路，很难控制数据转发到哪个链路

[R1]dis ip routing-table protocol isis
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Public routing table : ISIS
         Destinations : 1        Routes : 2        

ISIS routing table status : 
         Destinations : 1        Routes : 2

Destination/Mask                 Proto                Pre      Cost      Flag         NextHop         Interface

        0.0.0.0/0                     ISIS-L1             15        10          D             10.1.14.4       GigabitEthernet0/0/0
                                           ISIS-L1             15        10          D              10.1.12.2       Serial2/0/0

配置命令

可以在L2到L1做路由泄露，也可以控制从L1到L2的路由更新

需要L1/L2设备上完成（R2、R4）

L2到L1的路由泄漏

R2
isis 1
 network-entity 49.0124.2222.2222.2222.00
 import-route isis level-2 into level-1 filter-policy 2000

R4
isis 1
 network-entity 49.0124.4444.4444.4444.00
 import-route isis level-2 into level-1 filter-policy 2000
Basic ACL 2000, 2 rules
Acl's step is 5
 rule 10 permit source 20.20.20.20 0 (2 matches)
 rule 11 deny (1 matches)

dis ip routing-table protocol isis
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Public routing table : ISIS
         Destinations : 6        Routes : 8        

ISIS routing table status : 
         Destinations : 6        Routes : 8

Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

        0.0.0.0/0   ISIS-L1 15   10          D   10.1.12.2       Serial2/0/0
                    ISIS-L1 15   10          D   10.1.14.4       GigabitEthernet0/0/0
      10.1.20.0/24  ISIS-L1 15   20          D   10.1.12.2       Serial2/0/0
      10.1.40.0/24  ISIS-L1 15   20          D   10.1.14.4       GigabitEthernet0/0/0
    20.20.20.20/32  ISIS-L1 15   20          D   10.1.14.4       GigabitEthernet0/0/0
                              ISIS-L1 15   20          D   10.1.12.2       Serial2/0/0
       22.1.1.1/32  ISIS-L1 15   10          D   10.1.12.2       Serial2/0/0
       44.1.1.1/32  ISIS-L1 15   10          D   10.1.14.4       GigabitEthernet0/0/0 //华为设备这些L1/L2的直连无法做出控制（高端设备NE5000可以）。

L1到L2的路由控制

L1到L2的控制
R2、R4
[R4]isis
[R4-isis-1]import-route isis level-1 into level-2 filter-policy acl-name L1TOL2 tag 100 //仅仅把L1的符合条件的路由引入到L2,这些路由增加了管理TAG 100（注意需要wide的cost-style）
[R4]acl name L1TOL2 3999  
[R4-acl-adv-L1TOL2] rule 5 permit ip source 11.1.1.1 0
[SW2]dis ip routing-table protocol isis
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Public routing table : ISIS
         Destinations : 5        Routes : 6        

ISIS routing table status : 
         Destinations : 5        Routes : 6

Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

      10.1.12.0/24  ISIS-L2 15   20          D   10.1.20.2       Vlanif20
      10.1.14.0/24  ISIS-L2 15   20          D   10.1.40.4       Vlanif40
       11.1.1.1/32  ISIS-L2 15   20          D   10.1.20.2       Vlanif20
                    ISIS-L2 15   20          D   10.1.40.4       Vlanif40 //仅仅该路由被引入到L2
       22.1.1.1/32  ISIS-L2 15   10          D   10.1.20.2       Vlanif20
       44.1.1.1/32  ISIS-L2 15   10          D   10.1.40.4       Vlanif40
  
   
[SW2]dis ip routing-table 11.1.1.1 verbose 
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Table : Public
Summary Count : 2

Destination: 11.1.1.1/32
     Protocol: ISIS-L2         Process ID: 1
   Preference: 15                    Cost: 20
      NextHop: 10.1.20.2        Neighbour: 0.0.0.0
        State: Active Adv             Age: 00h01m53s
          Tag: 100 //如不修改cost-style wide，此处为0        Priority: medium
        Label: NULL               QoSInfo: 0x0
   IndirectID: 0x0              
 RelayNextHop: 0.0.0.0          Interface: Vlanif20
     TunnelID: 0x0                  Flags:  D

Destination: 11.1.1.1/32
     Protocol: ISIS-L2         Process ID: 1
   Preference: 15                    Cost: 20
      NextHop: 10.1.40.4        Neighbour: 0.0.0.0
        State: Active Adv             Age: 00h01m52s
          Tag: 100               Priority: medium
        Label: NULL               QoSInfo: 0x0
   IndirectID: 0x0              
 RelayNextHop: 0.0.0.0          Interface: Vlanif40
     TunnelID: 0x0                  Flags:  D
 
度量值范围
[R1-Serial2/0/0]isis cost ?        
  INTEGER<1-63>  Cost value   //默认情况是narrow的cost-style-->wide cost-style
对MPLS TE以及管理TAG的实现都需要wide的方式
[SW2-isis-1]cost-style wide       //所有在网设备都需要改变，否则路由计算出错
[SW2-Vlanif40]isis cost ?
  INTEGER<1-16777215>  Cost value
[SW2-LoopBack0]isis tag-value 20202020 //ISIS支持对该接口产生的路由直接增加管理2020202，而不用在引入（外部路由）的时候才能增加TAG