问题描述：
1、R1和R4的环回口均不参与路由协议，作为直连接口即可
2、R1到R4环回口实现负载均衡，即可以从R2到达，也可从R3到达
3、R4到R1环回口实现负载均衡，即可以从R2到达，也可从R3到达
思考：重分布时要注意避免环路，怎样设置重分布中的metic值比较好？
实验现象及分析：
当只把ospf重分布进eigrp时，R4路由表显示如下：
R4#show ip route
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
D EX 1.1.1.0 [170/284160] via 10.234.0.2, 00:01:45, FastEthernet0/0
[170/284160] via 10.234.0.3, 00:00:40, FastEthernet0/0
4.0.0.0/24 is subnetted, 1 subnets
C 4.4.4.0 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 1 subnets
C 10.234.0.0 is directly connected, FastEthernet0/0
12.0.0.0/30 is subnetted, 1 subnets
D EX 12.0.0.0 [170/284160] via 10.234.0.2, 00:01:45, FastEthernet0/0
[170/284160] via 10.234.0.3, 00:00:39, FastEthernet0/0
13.0.0.0/30 is subnetted, 1 subnets
D EX 13.0.0.0 [170/284160] via 10.234.0.2, 00:01:45, FastEthernet0/0
[170/284160] via 10.234.0.3, 00:00:39, FastEthernet0/0
由R4路由表可知，到达R1环回口可以通过R2或R3两条路径。
现在把eigrp重分布进ospf中后，R1路由表显示如下：
R1#show ip route
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Loopback0
4.0.0.0/24 is subnetted, 1 subnets
O E2 4.4.4.0 [110/20] via 12.0.0.2, 00:00:38, Serial0/0/0
10.0.0.0/24 is subnetted, 1 subnets
O E2 10.234.0.0 [110/20] via 13.0.0.2, 00:00:04, Serial0/0/1
12.0.0.0/30 is subnetted, 1 subnets
C 12.0.0.0 is directly connected, Serial0/0/0
13.0.0.0/30 is subnetted, 1 subnets
C 13.0.0.0 is directly connected, Serial0/0/1
由R1路由表可知，R1到达R4环回口只能通过R2，此时并没有实现负载均衡，原因何在？
看看R3的路由表先：
R3#show ip route
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
O E2 1.1.1.0 [110/20] via 13.0.0.1, 00:33:04, Serial0/0/0
4.0.0.0/24 is subnetted, 1 subnets
O E2 4.4.4.0 [110/20] via 13.0.0.1, 00:03:33, Serial0/0/0
10.0.0.0/24 is subnetted, 1 subnets
C 10.234.0.0 is directly connected, FastEthernet0/0
12.0.0.0/30 is subnetted, 1 subnets
O 12.0.0.0 [110/128] via 13.0.0.1, 00:34:53, Serial0/0/0
13.0.0.0/30 is subnetted, 1 subnets
C 13.0.0.0 is directly connected, Serial0/0/0对于后面这两句话表述不知道准不准确，如不对，还请大家多多指教）
（大家可以试试采用前一种修改办法，此时会有什么不同的效果。我做时到后来是不行的）
修改后R1和R4的路由表显示如下：
R1#show ip route
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Loopback0
4.0.0.0/24 is subnetted, 1 subnets
O E2 4.4.4.0 [110/20] via 13.0.0.2, 00:03:58, Serial0/0/1
[110/20] via 12.0.0.2, 00:03:58, Serial0/0/0
10.0.0.0/24 is subnetted, 1 subnets
O E2 10.234.0.0 [110/20] via 12.0.0.2, 00:34:13, Serial0/0/0
[110/20] via 13.0.0.2, 00:34:13, Serial0/0/1
12.0.0.0/30 is subnetted, 1 subnets
C 12.0.0.0 is directly connected, Serial0/0
13.0.0.0/30is subnetted, 1 subnets
C 13.0.0.0 is directly connected, Serial0/1
R4#show ip route
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
D EX 1.1.1.0 [170/307200] via 10.234.0.2, 00:05:34, FastEthernet0/0
[170/307200] via 10.234.0.3, 00:05:34, FastEthernet0/0 4.0.0.0/24 is subnetted, 1 subnets
C 4.4.4.0 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 1 subnets
C 10.234.0.0 is directly connected, FastEthernet0/0
12.0.0.0/30 is subnetted, 1 subnets
D EX 12.0.0.0 [170/307200] via 10.234.0.2, 00:01:45, FastEthernet0/0
[170/307200] via 10.234.0.3, 00:00:39, FastEthernet0/0
13.0.0.0/30 is subnetted, 1 subnets
D EX 13.0.0.0 [170/307200] via 10.234.0.2, 00:01:45, FastEthernet0/0
[170/307200] via 10.234.0.3, 00:00:39, FastEthernet0/0
用ping命令测试可通，用至此，完成实验目的。
本实验由于是在packettracer5上搭建的拓扑，在模拟Cisco2811路由器上不能完成修改重分布管理距离的命令，故最后采用在真实机上搭建拓扑并完成实验，结论如上所述。
先附上真实机上操作的配置。
如有不足，请各位多多指教。
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