要求：
1.如图连接，合理规划IP地址，所有路由器各自创建一个loopback接口
2.R1再创建三个接口IP地址为201.1.1.1/24、201.1.2.1/24、201.1.3.1/24
R5再创建三个接口IP地址为202.1.1.1/24、202.1.2.1/24、202.1.3.1/24
R7再创建三个接口IP地址为203.1.1.1/24、203.1.2.1/24、203.1.3.1/24
3.如图运行路由协议
R1 -R2 -R3之间使用MGRE网络，为hub-spoke 网络结构，R1为hub端 ，
部署OSPF网络,MGRE修改为BMA网络类型
4.area 1 区域不得出现4.5类LSA
5.其他区域优先通过R3访问R1 三个环回接口
6.尽量减少路由条目数量
7.area 1 区域增加安全性
8.全网可达
1、创建环回接口
分别在r1、r5、r7上创建要求的环回接口
[r1]interface LoopBack 0
[r1-LoopBack0]ip address 1.1.1.1 32
[r1-LoopBack0]ip address 201.1.1.1 24
[r1-LoopBack0]ip address 201.1.2.1 24
[r1-LoopBack0]ip address 201.1.3.1 24
运行ospf并且r1 r2 r3 运行MGRE
在r1上如下配置
[r1]interface Tunnel 0/0/0
[r1-Tunnel0/0/0]ip address 100.1.1.1 255.255.255.0
[r1-Tunnel0/0/0]tunnel-protocol gre p2mp
[r1-Tunnel0/0/0]source 18.1.1.1
Sep 16 2022 11:09:43-08:00 r1 %%01IFNET/4/LINK_STATE(l)[6]:The line protocol IP
on the interface Tunnel0/0/0 has entered the UP state.
[r1-Tunnel0/0/0]ospf network-type broadcast
[r1-Tunnel0/0/0]ospf dr-priority 100
[r1-Tunnel0/0/0]nhrp entry multicast dynamic
[r1-Tunnel0/0/0]nhrp network-id 100
在r2上如下配置，r3和r2配置基本相同
[r2]interface t0/0/0
[r2-Tunnel0/0/0]ip address 100.1.1.2 255.255.255.0
[r2-Tunnel0/0/0]tunnel-protocol gre p2mp
[r2-Tunnel0/0/0]source 28.1.1.2
Sep 16 2022 11:11:40-08:00 r2 %%01IFNET/4/LINK_STATE(l)[12]:The line protocol IP
on the interface Tunnel0/0/0 has entered the UP state.
[r2-Tunnel0/0/0]ospf network-type broadcast
[r2-Tunnel0/0/0]ospf dr-priority 0
[r2-Tunnel0/0/0]nhrp network-id 100
[r2-Tunnel0/0/0]nhrp entry 100.1.1.1 18.1.1.1 register
area 1 区域不得出现4.5类LSA
在r2 r3 r4分别进行如下配置，成为nssa区域
[r2]ospf 100
[r2-ospf-100]area 1
[r2-ospf-100-area-0.0.0.1]nssa
其他区域优先通过R3访问R1 三个环回接口
在R3和R4中使用tunnel将AREA 0区域扩大，防止R3路由器出现意外情况，在R2和R4中也要使用tunnle将AREA 0区域扩大。因为优先通过R3学习和访问 所以在R2与R4之间将cost的值修改变大
[r2-Tunnel0/0/2]ip address 150.1.1.1 255.255.255.0
[r2-Tunnel0/0/2]tunnel-protocol gre
[r2-Tunnel0/0/2]source 24.1.1.1s
[r2-Tunnel0/0/2]destination 24.1.1.2
Sep 16 2022 13:51:53-08:00 r2 %%01IFNET/4/LINK_STATE(l)[20]:The line protocol IP
on the interface Tunnel0/0/2 has entered the UP state.
[r2-Tunnel0/0/2]ospf cost 3999
[r3]interface t0/0/1
[r3-Tunnel0/0/1]ip address 200.1.1.0 255.255.255.0
[r3-Tunnel0/0/1]tunnel-protocol gre
[r3-Tunnel0/0/1]source 34.1.1.1
[r3-Tunnel0/0/1]destination 34.1.1.2
[r4]interface t0/0/1
[r4-Tunnel0/0/1]ip address 200.1.1.2 255.255.255.0g
[r4-Tunnel0/0/1]tunnel-protocol gre
[r4-Tunnel0/0/1]source 34.1.1.2
[r4-Tunnel0/0/1]destination 34.1.1.1
Sep 16 2022 13:54:13-08:00 r4 %%01IFNET/4/LINK_STATE(l)[34]:The line protocol IP
on the interface Tunnel0/0/1 has entered the UP state.
[r4]interface t0/0/2
[r4-Tunnel0/0/2]ip address 150.1.1.2 255.255.255.0
[r4-Tunnel0/0/2]tunnel-protocol gre
[r4-Tunnel0/0/2]source 24.1.1.2
[r4-Tunnel0/0/2]destination 24.1.1.1
Sep 16 2022 13:55:14-08:00 r4 %%01IFNET/4/LINK_STATE(l)[35]:The line protocol IP
on the interface Tunnel0/0/2 has entered the UP state.
[r4-Tunnel0/0/2]ospf cost 3999
area 1 区域增加安全性
在r2 r3 r4上面配置区域认证
[r2]ospf 100
[r2-ospf-100-area-0.0.0.1]authentication-mode simple plain 1234
在r2 r3 r4 r6下放缺省路由
[r3]ospf 100 router-id 3.3.3.3
[r3-ospf-100]default-route-advertise always
[r6]rip 100
[r6-rip-100]default-route originate
