拓扑很简单，就是两台路由器背对背
RouterA
interface ethernet 0
ip address 10.3.3.1 255.255.255.0
ip router isis
clns router isis
isis password SECr3t level-1
isis password SECr3t level-2
interface serial0
ip address 10.1.1.1 255.255.255.252
clns router isis
ip router isis
router isis
passive-interface Loopback0
passive-interface Loopback1
net 49.1234.1111.1111.1111.00
Router
interface ethernet 0
ip address 10.3.3.2 255.255.255.0
ip router isis
clns router isis
isis password SECr3t level-1
isis password SECr3t level-2
interface serial0
ip address 172.16.1.1 255.255.255.252ip router isis
clns router isis
router isis
passive-interface Loopback0
passive-interface Loopback1
net 49.1234.2222.2222.2222.00
补充说明
在同一IS-IS area 内，认证命令是
area-password xxxxx
在不同IS-IS area中，认证命令是
domain-password