本实验模拟ISP的双栈：
上面是v4网络，下面是v6网络R1 R4启用双栈 分析为什么需要多拓扑 因为R1的g0/0/0接口的cost=1，此时根据SPF最短路径树算R1去往R4都走R1-R2-R4 因为使用的是同一张拓扑导致V6网络没有走下面，导致无法到达 所以我们在R1 R4上面启用拓扑 参考配置： ip topology v4 ipv6 topology v6 #创建V4 V6拓扑 isis 1 is-level level-2 cost-style wide network-entity 49.0001.0000.0000.0001.00 # ipv6 enable topology ipv6 #启用V6拓扑 topology v4 topology-id 40 ipv6 topology v6 topology-id 60 #给V4 V6 拓扑绑定一个ID interface GigabitEthernet0/0/0 ip address 12.1.1.1 255.255.255.0 ip topology v4 enable #在对应接口下启用拓扑 isis enable 1 isis cost 1 # interface GigabitEthernet0/0/1 ipv6 enable ipv6 topology v6 enable #在对应接口下启用拓扑 ipv6 address auto link-local isis ipv6 enable 1 #开启isis的v6功能 isis ipv6 topology v6 #开启isis ipv6拓扑 interface LoopBack0 ipv6 enable ip address 1.1.1.1 255.255.255.255 ip topology v4 enable ipv6 topology v6 enable ipv6 address 3000::1/128 ipv6 address auto link-local isis enable 1 isis ipv6 enable 1 isis ipv6 topology v6检查结果
