Question request ：

  Problem analysis ：

1、 Subnet partition topology

2、 Configure router loopback address and interface ip

AR1
<Huawei>system-view 
<Huawei>sysname r1
<r1>int loopBack 1
[r1-LoopBack1]ip add 192.168.1.65 26
[r1-LoopBack1]q
[r1]int GigabitEthernet 0/0/0
[r1-GigabitEthernet0/0/0]ip address 192.168.1.1 29

AR2

<Huawei>system-view 
[Huawei]sysname r2
[r2]int LoopBack 1
[r2-LoopBack1]ip address 192.168.1.129 26
[r2-LoopBack1]int g0/0/0 
[r2-GigabitEthernet0/0/0]ip address 192.168.1.2 29

AR3

<Huawei>system-view 
[Huawei]sysname r3
[r3]int LoopBack 1
[r3-LoopBack1]ip address 192.168.1.193 26
[r3-LoopBack1]int g0/0/0
[r3-GigabitEthernet0/0/0]ip address 192.168.1.3 29
[r3-GigabitEthernet0/0/0]int g0/0/1
[r3-GigabitEthernet0/0/1]ip address 192.168.1.9 29

AR4

<Huawei>system-view 
[Huawei]sysname r4
[r4]int LoopBack 1
[r4-LoopBack1]ip address 4.4.4.4 24
[r4-LoopBack1]int g0/0/0  
[r4-GigabitEthernet0/0/0]ip address 192.168.1.10 29

3、 start-up ospf And declare

AR1

[r1]ospf 1 router-id 1.1.1.1 
[r1-ospf-1]area 0
[r1-ospf-1-area-0.0.0.0]network 192.168.1.65 0.0.0.0
[r1-ospf-1-area-0.0.0.0]network 192.168.1.1 0.0.0.0

AR2

[r2]ospf 1 router-id 2.2.2.2  
[r2-ospf-1]area 0 
[r2-ospf-1-area-0.0.0.0]network 192.168.1.129 0.0.0.0
[r2-ospf-1-area-0.0.0.0]network 192.168.1. 2  0.0.0.0

AR3

[r3]ospf 1 router-id 3.3.3.3   
[r3-ospf-1]area 0  
[r3-ospf-1-area-0.0.0.0]network 192.168.1.193 0.0.0.0
[r3-ospf-1-area-0.0.0.0]network 192.168.1.3 0.0.0.0
[r3-ospf-1-area-0.0.0.0]q 
[r3-ospf-1]area 1    
[r3-ospf-1-area-0.0.0.1]network 192.168.1.9 0.0.0.0
 

AR4

[r4]ospf 1 router-id 4.4.4.4
[r4-ospf-1]area 1
[r4-ospf-1-area-0.0.0.1]network 192.168.1.10 0.0.0.0

4、AR3 by DR equipment , No, BDR equipment , take AR1、AR2、AR3 The interface priority of is set to 0 that will do

[r1-GigabitEthernet0/0/0]ospf dr-priority 0

[r2-GigabitEthernet0/0/0]ospf dr-priority 0

[r4-GigabitEthernet0/0/0]ospf dr-priority 0

see ospf

 5、 Network wide accessibility ,R4 Changing back address cannot announce

          Need to be AR4 Configuration on router Default route

[r4-ospf-1]default-route-advertise always 

see AR3 Routing table
 

        Be careful ：AR2、AR1 similar

6、 To ensure the security of updates

          Configure authentication on each router interface

[r1-GigabitEthernet0/0/0]ospf authentication-mode md5 1 cipher 123456

[r2-GigabitEthernet0/0/0]ospf authentication-mode md5 1 cipher 123456

[r3-GigabitEthernet0/0/0]ospf authentication-mode md5 1 cipher 123456

[r3-GigabitEthernet0/0/1]ospf authentication-mode md5 1 cipher 123456

[r4-GigabitEthernet0/0/0]ospf authentication-mode md5 1 cipher 123456

7、 Avoid loops and reduce the number of routing entries

Yes ip Conduct area （0 and 1） Summary , Area 1 There is only one route in , There is no need to summarize

r3]ospf 1
[r3-ospf-1]ar 0
[r3-ospf-1-area-0.0.0.0]abr-summary 192.168.1.0 255.255.255.0

see AR4 Routing table

  verification