实验目标：
1.R1、R2和R3均采用EIGRP 100；
2.R2、R4采用OSPF 98 Area 24；
3.R3、R4采用OSPF 98 Area 34；
4.R4的Loopback0为OSPF 98 Area 0。
5.现需从R1到到R4的Loopback0优先路径为R1->R2->R3->R4，当R3挂死后，R1去到R4的路径为R1->R2->R4。
R1: interface FastEthernet0/0 ip address 192.168.12.1 255.255.255.0 router eigrp 100 network 192.168.12.0 R2: interface FastEthernet0/0 ip address 192.168.12.2 255.255.255.0 interface Serial0/0 ip address 192.168.24.2 255.255.255.0 interface FastEthernet0/1 ip address 192.168.23.2 255.255.255.0 router eigrp 100 redistribute ospf 98 metric 100000 10 255 1 1500 network 192.168.12.0 network 192.168.23.0 distance eigrp 90 90 router ospf 98 router-id 2.2.2.2 log-adjacency-changes redistribute eigrp 100 subnets network 192.168.24.0 0.0.0.255 area 24 R3: interface FastEthernet0/1 ip address 192.168.23.3 255.255.255.0 interface Serial0/1 ip address 192.168.34.3 255.255.255.0 router eigrp 100 redistribute ospf 98 metric 100000 10 255 1 1500 network 192.168.23.0 router ospf 98 router-id 3.3.3.3 log-adjacency-changes redistribute eigrp 100 subnets network 192.168.34.0 0.0.0.255 area 34 R4: interface Loopback0 ip address 172.16.100.1 255.255.255.0 interface Serial0/0 ip address 192.168.24.4 255.255.255.0 interface Serial0/1 ip address 192.168.34.4 255.255.255.0 router ospf 98 router-id 4.4.4.4 log-adjacency-changes network 172.16.100.0 0.0.0.255 area 0 network 192.168.24.0 0.0.0.255 area 24 network 192.168.34.0 0.0.0.255 area 34