双向重发布实验
需求：
首先画出拓扑图
将地址进行配置
配置完成后进行双向重发布；
这时发现R1-3上出现两个4.4.4.0网段，这是因为ospf在学习回环路由时默认学习32位主机路由；而R4直连导入rip中为掩码24位；这时就会产生不同的网段
解决方法：
1.将环回掩码修改为32位
2.将环回ospf工作方式修改为broadcast
这里我使用的是修改环回ospf结构工作类型
[r4-LoopBack0]ospf network-type broadcast
这时还会发现选路不佳：
会发现虽然解决掩码不同的问题；但是在R1访问R4环回时，当然是通过R4访问选路更佳；总之，上边的链路相关网段应该都经过上边；下边的链路相关网段应该都经过下边；还需注意题目要求有备份路径，所以不能将选路不佳的网段“”干掉”
[r2]ip ip-prefix a permit 34.1.1.0 24
[r2]ip ip-prefix b permit 4.4.4.0 24
[r2]route-policy ospf1 permit node 10
Info: New Sequence of this List.
[r2-route-policy]if-match ip-prefix a
[r2-route-policy]apply cost 170
[r2-route-policy]q
[r2]route-policy ospf1 permit node 20
Info: New Sequence of this List.
[r2-route-policy]if-match ip-prefix b
[r2-route-policy]apply cost 170
[r2-route-policy]q
[r2]rip 1
[r2-rip-1]import-route ospf 1 route-policy ospf1
[r2-rip-1]q
[r2]ip ip-prefix c permit 14.1.1.0 24
[r2]route-policy rip1 permit node 10
Info: New Sequence of this List.
[r2-route-policy]if-match ip-prefix c
[r2-route-policy]apply cost 170
[r2-route-policy]q
[r2]route-policy rip1 permit node 20
Info: New Sequence of this List.
[r2-route-policy]q
[r2]route-policy ospf1 permit node 30
Info: New Sequence of this List.
[r2-route-policy]q
[r2]ospf 1
[r2-ospf-1]import-route rip 1 route-policy rip1
[r4]ip ip-prefix a permit 12.1.1.0 24
[r4]ip ip-prefix b permit 2.2.2.0 24
[r4]route-policy rip2 permit node 10
Info: New Sequence of this List.
[r4-route-policy]if-match ip-prefix a
[r4-route-policy]apply cost 170
[r4-route-policy]q
[r4]route-policy rip2 permit node 20
Info: New Sequence of this List.
[r4-route-policy]if-match ip-prefix b
[r4-route-policy]apply cost 170
[r4-route-policy]q
[r4]route-policy rip2 permit node 30
Info: New Sequence of this List.
[r4-route-policy]q
[r4]ospf 1
[r4-ospf-1]import-route rip 1 route-policy rip2
[r4-ospf-1]q
[r4]ip ip-prefix c permit 23.1.1.0 24
[r4]route-policy ospf2 permit node 10
Info: New Sequence of this List.
[r4-route-policy]if-match ip-prefix c
[r4-route-policy]apply cost 170
[r4-route-policy]q
[r4]route-policy ospf2 permit node 20
Info: New Sequence of this List.
[r4-route-policy]q
[r4]rip 1
[r4-rip-1]import-route ospf 1 route-policy ospf2
[r4-rip-1]q
这时查看R1和R4路由表，发现R1和R4环回负载均衡，其他选路最佳。自此实验完成！