实验要求：掌握基于链路的OSPFMD5口令认证
拓扑如下：
配置如下：
R1
enable
configure terminal
interface s0/0/0
ip address 192.168.1.1 255.255.255.0
no shutdown
clock rate 64000
interface l0
ip address 1.1.1.1 255.255.255.0
exit
router ospf 1
network 192.168.1.0 0.0.0.255 area 0
network 1.1.1.0 0.0.0.255 area 0
interface s0/0/0
ip ospf authentication message-digest
ip ospf message-digest-key 1 md5 123
R2
enable
configure terminal
interface s0/0/0
ip address 192.168.1.2 255.255.255.0
no shutdown
clock rate 64000
interface l0
ip address 2.2.2.2 255.255.255.0
exit
router ospf 1
network 192.168.1.0 0.0.0.255 area 0
network 2.2.2.0 0.0.0.255 area 0
interface s0/0/0
ip ospf authentication message-digest
ip ospf message-digest-key 1 md5 123