实验如下图示：
R1: interface Loopback0 ip address 172.16.2.1 255.255.255.0 secondary ip address 172.16.1.1 255.255.255.0 ip router isis isis circuit-type level-1 interface Serial1/1 ip address 172.16.255.1 255.255.255.252 ip router isis serial restart-delay 0 isis circuit-type level-2-only router isis net 49.0001.ca00.0bbc.0000 is-type level-1-2 //一般缺省值为level-1-2,不会显示出来 R2: interface Serial1/0 ip address 172.16.255.2 255.255.255.252 ip router isis isis circuit-type level-1-2 //一般缺省值为level-1-2,不会显示出来 interface Serial1/1 ip address 172.16.255.5 255.255.255.252 ip router isis isis circuit-type level-2-only router isis net 49.0002.ca01.0bbc.0000 R3: interface Serial1/0 ip address 172.16.255.6 255.255.255.252 ip router isis interface Serial1/1 ip address 172.16.255.9 255.255.255.252 ip router isis isis circuit-type level-2-only router isis net 49.0002.ca02.0bbc.0000 R4: interface Serial1/0 ip address 172.16.255.10 255.255.255.252 ip router isis isis circuit-type level-2-only interface Serial1/1 ip address 172.16.255.13 255.255.255.252 ip router isis router isis net 49.0003.ca03.0bbc.0000 R5: interface Loopback0 ip address 172.16.128.1 255.255.255.0 ip router isis isis circuit-type level-1 interface Loopback1 ip address 172.16.129.1 255.255.255.0 ip router isis interface Serial1/0 ip address 172.16.255.14 255.255.255.252 ip router isis router isis net 49.0003.ca04.0bbc.0000 R5#show ip route isis 172.16.0.0/16 is variably subnetted, 8 subnets, 2 masks i L2 172.16.255.0/30 [115/40] via 172.16.255.13, Serial1/0 i L2 172.16.255.4/30 [115/30] via 172.16.255.13, Serial1/0 i L2 172.16.255.8/30 [115/20] via 172.16.255.13, Serial1/0 i L2 172.16.1.0/24 [115/50] via 172.16.255.13, Serial1/0 i L2 172.16.2.0/24 [115/50] via 172.16.255.13, Serial1/0 R1#show ip route isis 172.16.0.0/16 is variably subnetted, 8 subnets, 2 masks i L2 172.16.128.0/24 [115/50] via 172.16.255.2, Serial1/1 i L2 172.16.129.0/24 [115/50] via 172.16.255.2, Serial1/1 i L2 172.16.255.4/30 [115/20] via 172.16.255.2, Serial1/1 i L2 172.16.255.8/30 [115/30] via 172.16.255.2, Serial1/1 i L2 172.16.255.12/30 [115/40] via 172.16.255.2, Serial1/1 R1#ping 172.16.128.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.128.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 48/60/88 ms R5#ping 172.16.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 60/73/84 ms
R1: router isis summary-address 172.16.0.0 255.255.252.0 R4: show ip route isis 172.16.0.0/16 is variably subnetted, 7 subnets, 3 masks i L1 172.16.128.0/24 [115/20] via 172.16.255.14, Serial1/1 i L1 172.16.129.0/24 [115/20] via 172.16.255.14, Serial1/1 i L2 172.16.255.0/30 [115/30] via 172.16.255.9, Serial1/0 i L2 172.16.255.4/30 [115/20] via 172.16.255.9, Serial1/0 i L2 172.16.0.0/22 [115/40] via 172.16.255.9, Serial1/0