写在前面：双点双向路由重发布是一个经典的课题，这种类型的组网很容易出现路由环路或者次优路径的问题。解决的方法也是多种多样的，我们这里先演示一种：修改路由优先级。由于OSPF内部优先级为10 外部优先级为150，当把rip路由重发布到OSPF中时由于rip优先级为100会出现次优路径。
1.拓扑图
链接：https://pan.baidu.com/s/1bwD4f3TNcFzLBENIjw4NMQ
提取码：8888
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链接：https://pan.baidu.com/s/1wP0vHim4yqVV0bc0wmzhFw
提取码：8888
2、网络需求
a. R1、R2及R3运行OSPF；R2、R3、R4运行RIPv2；
b. R1创建一个Loopback0接口，配置IP地址1.1.1.1/32，并且将这个接口的直连路由重发布到OSPF；
c. 在R2及R3上均执行双向的路由重发布，也就是将OSPF路由注入到RIP，将RIP路由注入到OSPF，本路由域内的网段需通过该路由协议的路由到达，不能出现次优路径。
3.配置
在R2及R3上执行双向路由重发布
R2的配置如下：
[R2] ospf 1
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[R2-ospf-1] import-route rip
[R2] rip
[R2-rip-1] import-route ospf 1
R3的配置如下：
[R3] ospf 1
[R3-ospf-1] import-route rip
[R3] rip
[R3-rip-1] import-route ospf 1
在R2及R3上，
创建一个前缀列表1用于抓取1.1.1.1/32这条OSPF外部路由，然后在route-policy ase中调用该条ACL，并将匹配这条ACL的路由的优先级值设置为99（比RIP路由的优先级100更小），然后在OSPF的视图下使用preference命令调用这个route-policy。OSPF视图下的Preference ase这条命令用于修改外部路由（ase）的优先级。
R2的配置如下：
[R2] ip ip-prefix 1 permit 1.1.1.1 32
[R2] route-policy ase_policy permit node 10
[R2-route-policy] if-match ip-prefix 1
[R2-route-policy] apply preference 99
[R2] ospf 1
[R2-ospf-1] preference ase route-policy ase_policy
R3的配置如下：
[R3] ip ip-prefix 1 permit 1.1.1.1 32
[R3] route-policy ase_policy permit node 10
[R3-route-policy] if-match ip-prefix 1
[R3-route-policy] apply preference 99
[R3] ospf 1
[R3-ospf-1] preference ase route-policy ase_policy
3.1 R1的配置
display current-configuration
sysname R1
aaa
authentication-scheme default
authorization-scheme default
accounting-scheme default
domain default
domain default_admin
local-user admin password cipher OOCM4m($F4ajUn1vMEIBNUw#
local-user admin service-type http
firewall zone Local
priority 16
interface Ethernet0/0/0
interface Ethernet0/0/1
interface Serial0/0/0
link-protocol ppp
interface Serial0/0/1
link-protocol ppp
interface Serial0/0/2
link-protocol ppp
interface Serial0/0/3
link-protocol ppp
interface GigabitEthernet0/0/0
ip address 192.168.12.1 255.255.255.0
interface GigabitEthernet0/0/1
ip address 192.168.13.1 255.255.255.0
interface GigabitEthernet0/0/2
interface GigabitEthernet0/0/3
wlan
interface NULL0
interface LoopBack0
ip address 1.1.1.1 255.255.255.255
ospf 1 router-id 1.1.1.1
import-route direct
area 0.0.0.0
network 192.168.12.0 0.0.0.255
network 192.168.13.0 0.0.0.255
user-interface con 0
user-interface vty 0 4
user-interface vty 16 20
return
3.2 R2的配置
display current-configuration
sysname R2
aaa
authentication-scheme default
authorization-scheme default
accounting-scheme default
domain default
domain default_admin
local-user admin password cipher OOCM4m($F4ajUn1vMEIBNUw#
local-user admin service-type http
firewall zone Local
priority 16
interface Ethernet0/0/0
interface Ethernet0/0/1
interface Serial0/0/0
link-protocol ppp
interface Serial0/0/1
link-protocol ppp
interface Serial0/0/2
link-protocol ppp
interface Serial0/0/3
link-protocol ppp
interface GigabitEthernet0/0/0
ip address 192.168.12.2 255.255.255.0
interface GigabitEthernet0/0/1
ip address 192.168.24.2 255.255.255.0
interface GigabitEthernet0/0/2
interface GigabitEthernet0/0/3
wlan
interface NULL0
ospf 1 router-id 2.2.2.2
import-route rip 1
preference ase route-policy ase 150
area 0.0.0.0
network 192.168.12.0 0.0.0.255
rip 1
undo summary
version 2
network 192.168.24.0
import-route ospf 1
route-policy ase permit node 10
if-match ip-prefix 1
apply preference 99
ip ip-prefix 1 index 10 permit 1.1.1.1 32
user-interface con 0
user-interface vty 0 4
user-interface vty 16 20
return
3.3 R3的配置
display current-configuration
sysname R3
aaa
authentication-scheme default
authorization-scheme default
accounting-scheme default
domain default
domain default_admin
local-user admin password cipher OOCM4m($F4ajUn1vMEIBNUw#
local-user admin service-type http
firewall zone Local
priority 16
interface Ethernet0/0/0
interface Ethernet0/0/1
interface Serial0/0/0
link-protocol ppp
interface Serial0/0/1
link-protocol ppp
interface Serial0/0/2
link-protocol ppp
interface Serial0/0/3
link-protocol ppp
interface GigabitEthernet0/0/0
ip address 192.168.13.3 255.255.255.0
interface GigabitEthernet0/0/1
ip address 192.168.34.3 255.255.255.0
interface GigabitEthernet0/0/2
interface GigabitEthernet0/0/3
wlan
interface NULL0
ospf 1 router-id 3.3.3.3
import-route rip 1
preference ase route-policy ase 150
area 0.0.0.0
network 192.168.13.0 0.0.0.255
rip 1
undo summary
version 2
network 192.168.34.0
import-route ospf 1
route-policy ase permit node 10
if-match ip-prefix 1
apply preference 99
ip ip-prefix 1 index 10 permit 1.1.1.1 32
user-interface con 0
user-interface vty 0 4
user-interface vty 16 20
return
3.4 R4的配置
display current-configuration
sysname R4
aaa
authentication-scheme default
authorization-scheme default
accounting-scheme default
domain default
domain default_admin
local-user admin password cipher OOCM4m($F4ajUn1vMEIBNUw#
local-user admin service-type http
firewall zone Local
priority 16
interface Ethernet0/0/0
interface Ethernet0/0/1
interface Serial0/0/0
link-protocol ppp
interface Serial0/0/1
link-protocol ppp
interface Serial0/0/2
link-protocol ppp
interface Serial0/0/3
link-protocol ppp
interface GigabitEthernet0/0/0
ip address 192.168.24.4 255.255.255.0
interface GigabitEthernet0/0/1
ip address 192.168.34.4 255.255.255.0
interface GigabitEthernet0/0/2
interface GigabitEthernet0/0/3
wlan
interface NULL0
rip 1
version 2
network 192.168.24.0
network 192.168.34.0
user-interface con 0
user-interface vty 0 4
user-interface vty 16 20
return
4.查看R3的路由表情况没有出现次优路径
