HCIP-18.5 双点双向 路由引入

避免路由环路：

R2：

isis 1
 import-route ospf 1 route-policy O2I

 #

route-policy O2I deny node 10
 if-ma tag 11
route-policy O2I per no 20
 apply tag 44

R1、R2、R3、R5：

isis 1
 cost-style wide  # 需要携带标签，isis需要修改为宽度量

R3：

ospf 1
 import-route isis 1 route-policy I2O
 #
route-policy I2O deny node 10
 if-ma tag 44 
route-policy I2O per no 20
 app tag 11

R3：

isis 1
 import-route ospf 1 route-policy O2I
 #
route-policy O2I deny no 10
 if-ma tag 11
route-policy O2I per no 20
 app tag 44

R1：

ospf 1
 import-route isis 1 route-policy I2O

#

route-policy I2O den no 10
 if-ma tag 44
route-policy I2O per no 20
 app tag 11

R2、R3次优路径问题

R2到达6.6.6.0/24次优路径问题

R2：

isis 1
 perference 170

此时，R2到达1.1.1.1 又会出现次优路径问题

R2：

isis 1
 preference route-policy PRE
 #

route-policy PRE per no 10
 if-ma tag 44
 apply prefercence 175
route-policy PRE per no 20

R3：

isis 1
 isis 1
 preference route-policy PRE
 #

route-policy PRE per no 10
 if-ma tag 44
 apply prefercence 175
route-policy PRE per no 20