目录
第一章 OSPF协议特性与配置
实验 1-1 OSPF单区域
学习目的
·掌握单区域OSPF的配置方法
·掌握OSPF区域认证的配置方法
·了解OSPF在多路访问网络邻居关系建立的过程
·理解OSPF对Loopback接口所连接网络的掩码发布的形式
·掌握对OSPF接口代价值进行修改的方法
·掌握OSPF中Silent-interface的配置方法
·掌握使用Display查看OSPF各种状态的方法
·掌握使用Debug命令查看OSPF邻接关系和进行故障排除的方法
拓扑图
图1-1 OSPF单区域
场景
你是公司的网络管理员。现在公司的网络中有三台ARG3路由器，通过以太网实现相互的连通。在以太网这样的广播式多路访问网络上，可能存在安全隐患，所有你选择采用OSPF区域认证的方法来避免恶意的路由攻击。在部署网络的过程中，出现了网络连通性的问题，你通过使用display和debug命令进行了故障排除。
学习任务
步骤一.基础配置与IP编址
给R1、R2和R3配置IP地址和掩码。配置时Loopback接口配置掩码为24位，模拟成一个单独的网段。配置完成后，测试直连链路的连通性。
<R1>system-view
Enter system view, return user view with Ctrl+Z.
[R1]interface GigabitEthernet 0/0/0
[R1-GigabitEthernet0/0/0]ip address 10.0.123.1 24
[R1-GigabitEthernet0/0/0]quit
[R1]interface LoopBack 0
[R1-LoopBack0]ip address 10.0.1.1 24
[R1-LoopBack0]quit
<R2>system-view
Enter system view, return user view with Ctrl+Z.
[R2]interface GigabitEthernet 0/0/0
[R2-GigabitEthernet0/0/0]ip address 10.0.123.2 24
[R2-GigabitEthernet0/0/0]quit
[R2]interface LoopBack 0
[R2-LoopBack0]ip address 10.0.2.2 24
[R2-LoopBack0]quit
<R3>system-view
Enter system view, return user view with Ctrl+Z.
[R3]interface GigabitEthernet 0/0/0
[R3-GigabitEthernet0/0/0]ip address 10.0.123.3 24
[R3-GigabitEthernet0/0/0]quit
[R3]interface LoopBack 0
[R3-LoopBack0]ip address 10.0.3.3 24
[R3-LoopBack0]quit
配置完各接口地址之后验证路由器之间的连通性。
[R1]ping -c 1 10.0.123.2
PING 10.0.123.2: 56 data bytes, press CTRL_C to break
Reply from 10.0.123.2: bytes=56 Sequence=1 ttl=255 time=2 ms
--- 10.0.123.2 ping statistics ---
1 packet(s) transmitted
1 packet(s) received
0.00% packet loss
round-trip min/avg/max = 2/2/2 ms
[R1]ping -c 1 10.0.123.3
PING 10.0.123.3: 56 data bytes, press CTRL_C to break
Reply from 10.0.123.3: bytes=56 Sequence=1 ttl=255 time=2 ms
--- 10.0.123.3 ping statistics ---
1 packet(s) transmitted
1 packet(s) received
0.00% packet loss
round-trip min/avg/max = 2/2/2 ms
[R2]ping -c 1 10.0.123.3
PING 10.0.123.3: 56 data bytes, press CTRL_C to break
Reply from 10.0.123.3: bytes=56 Sequence=1 ttl=255 time=2 ms
--- 10.0.123.3 ping statistics ---
1 packet(s) transmitted
1 packet(s) received
0.00% packet loss
round-trip min/avg/max = 2/2/2 ms
步骤二.配置单区域的OSPF
配置单区域OSPF。所有路由器属于区域0，配置使用OSPF进程1。同时配置区域认证，使用密码“huawei“。在区域中，华为的设备支持使用明文或MD5值进行认证，在这里，我们仅使用明文进行认证。
注意在使用network命令时，通配符掩码使用0.0.0.0。为了保证路由器的Router ID稳定，我们在启动OSPF进程时使用router-id参数静态指定路由器的Router ID。
[R1]ospf 1 router-id 10.0.1.1
[R1-ospf-1]area 0
[R1-ospf-1-area-0.0.0.0]network 10.0.123.1 0.0.0.0
[R1-ospf-1-area-0.0.0.0]network 10.0.1.1 0.0.0.0
[R1-ospf-1-area-0.0.0.0]authentication-mode simple plain huawei
[R1-ospf-1-area-0.0.0.0]quit
[R1-ospf-1]quit
[R2]ospf 1 router-id 10.0.2.2
[R2-ospf-1]area 0
[R2-ospf-1-area-0.0.0.0]network 10.0.123.2 0.0.0.0
[R2-ospf-1-area-0.0.0.0]network 10.0.2.2 0.0.0.0
[R2-ospf-1-area-0.0.0.0]authentication-mode simple plain huawei
[R2-ospf-1-area-0.0.0.0]quit
[R2-ospf-1]quit
[R3]ospf 1 router-id 10.0.3.3
[R3-ospf-1]area 0
[R3-ospf-1-area-0.0.0.0]network 10.0.123.3 0.0.0.0
[R3-ospf-1-area-0.0.0.0]network 10.0.3.3 0.0.0.0
[R3-ospf-1-area-0.0.0.0]authentication-mode simple plain huawei
[R3-ospf-1-area-0.0.0.0]quit
[R3-ospf-1]quit
配置完成后，查看设备的路由表，并测试全网的连通性。我们首先在R1上查看路由表。
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.2.2/32 OSPF 10 1 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.3/32 OSPF 10 1 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
从输出中我们可以看到R1从OSPF学习到了2条路由，10.0.2.2/32和10.0.3.3/32，下一跳分别是10.0.123.2和10.0.123.3。然后分别检查从R1到达R2及R3的Loopback地址的连通性。
[R1]ping -c 1 10.0.2.2
PING 10.0.2.2: 56 data bytes, press CTRL_C to break
Reply from 10.0.2.2: bytes=56 Sequence=1 ttl=255 time=3 ms
--- 10.0.2.2 ping statistics ---
1 packet(s) transmitted
1 packet(s) received
0.00% packet loss
round-trip min/avg/max = 3/3/3 ms
[R1]ping -c 1 10.0.3.3
PING 10.0.3.3: 56 data bytes, press CTRL_C to break
Reply from 10.0.3.3: bytes=56 Sequence=1 ttl=255 time=2 ms
--- 10.0.3.3 ping statistics ---
1 packet(s) transmitted
1 packet(s) received
0.00% packet loss
round-trip min/avg/max = 2/2/2 ms
使用display ospf brief命令查看路由器运行的基本OSPF信息。
[R1]display ospf brief
OSPF Process 1 with Router ID 10.0.1.1
OSPF Protocol Information
RouterID: 10.0.1.1 Border Router:
Multi-VPN-Instance is not enabled
Global DS-TE Mode: Non-Standard IETF Mode
Graceful-restart capability: disabled
Helper support capability : not configured
Applications Supported: MPLS Traffic-Engineering
Spf-schedule-interval: max 10000ms, start 500ms, hold 1000ms
Default ASE parameters: Metric: 1 Tag: 1 Type: 2
Route Preference: 10
ASE Route Preference: 150
SPF Computation Count: 9
RFC 1583 Compatible
Retransmission limitation is disabled
Area Count: 1 Nssa Area Count: 0
ExChange/Loading Neighbors: 0
Process total up interface count: 2
Process valid up interface count: 1
Area: 0.0.0.0 (MPLS TE not enabled)
Authtype: Simple Area flag: Normal
SPF scheduled Count: 9
ExChange/Loading Neighbors: 0
Router ID conflict state: Normal
Area interface up count: 2
Interface: 10.0.1.1 (LoopBack0)
Cost: 0 State: P-2-P Type: P2P MTU: 1500
Timers: Hello 10 , Dead 40 , Poll 120 , Retransmit 5 , Transmit Delay 1
Interface: 10.0.123.1 (GigabitEthernet0/0/0)
Cost: 1 State: DR Type: Broadcast MTU: 1500
Priority: 1
Designated Router: 10.0.123.1
Backup Designated Router: 10.0.123.2
Timers: Hello 10 , Dead 40 , Poll 120 , Retransmit 5 , Transmit Delay 1
从上面的输出中我们可以看到区域0开启了明文认证（Authtype: Simple），共有两个接口参加了OSPF的运行：GigabitEthernet0/0/0和LoopBack0。其中，GigabitEthernet0/0/0为广播型网络（Broadcast），开销（Cost）为1，优先级（Priority）为1，R1自己的角色为DR，后面列出了该网络上的BDR（10.0.123.2）。另外一个运行OSPF的接口LoopBack0的网络类型为P2P。
使用display ospf peer brief命令查看路由器的OSPF邻居关系建立情况。
[R1]display ospf peer brief
OSPF Process 1 with Router ID 10.0.1.1
Peer Statistic Information
----------------------------------------------------------------------------
Area Id Interface Neighbor id State
0.0.0.0 GigabitEthernet0/0/0 10.0.2.2 Full
0.0.0.0 GigabitEthernet0/0/0 10.0.3.3 Full
----------------------------------------------------------------------------
Total Peer(s): 2
从上面的输出中我们可以看到在区域0.0.0.0中，R1有两个邻居，邻居的Router ID分别为10.0.2.2和10.0.3.3，他们之间的状态为Full。
使用display ospf lsdb命令查看路由器的OSPF数据库信息。
[R1]display ospf lsdb
OSPF Process 1 with Router ID 10.0.1.1
Link State Database
Area: 0.0.0.0
Type LinkState ID AdvRouter Age Len Sequence Metric
Router 10.0.3.3 10.0.3.3 1569 48 80000005 0
Router 10.0.2.2 10.0.2.2 1568 48 80000006 0
Router 10.0.1.1 10.0.1.1 1567 48 80000008 0
Network 10.0.123.110.0.1.1 1567 36 80000004 0
在这里我们一共可以看到4条LSA，前3条为第一类LSA，分别由R1、R2和R3产生，我们可以通过AdvRouter判断该LSA是由哪台路由器生成的。第四条为第二类LSA，是由一个网段的DR产生的。在这里，R1是10.0.123.0/24这个网段的DR，所以我们可以看到这条LSA的AdvRouter为10.0.1.1。
[R1]display ospf lsdb router self-originate
OSPF Process 1 with Router ID 10.0.1.1
Area: 0.0.0.0
Link State Database
Type : Router
Ls id : 10.0.1.1
Adv rtr : 10.0.1.1
Ls age : 430
Len : 48
Options : E
seq# : 80000009
chksum : 0x8188
Link count: 2
* Link ID: 10.0.1.1
Data : 255.255.255.255
Link Type: StubNet
Metric : 0
Priority : Medium
* Link ID : 10.0.123.1
Data : 10.0.123.1
Link Type: TransNet
Metric : 1
上面的输出是R1产生的Router LSA的详细信息，我们可以看到这条LSA一共描述了2个网络，第一个网络为Loopback接口所在网段，链路类型为StubNet，Link ID和Data分别是该Stub网段的IP地址和掩码。第二个网络为三台路由器的互联网段，链路类型为TransNet，可以看到Link ID为DR的端口地址10.0.123.1，Data为该网段上本地端口的IP地址10.0.123.1；
[R1]display ospf lsdb network self-originate
OSPF Process 1 with Router ID 10.0.1.1
Area: 0.0.0.0
Link State Database
Type : Network
Ls id : 10.0.123.1
Adv rtr : 10.0.1.1
Ls age : 1662
Len : 36
Options : E
seq# : 80000005
chksum : 0x3d58
Net mask : 255.255.255.0
Priority : Low
Attached Router 10.0.1.1
Attached Router 10.0.2.2
Attached Router 10.0.3.3
上面的输出是R1产生的Network LSA的详细信息，我们可以看到第二类LSA描述了DR所在网段的邻居信息。
步骤三.观察路由器在以太网上邻接关系的建立过程
首先查看在10.0.123.0/24网段，OSPF邻居关系中DR和BDR选举的情况，并分析为什么会这样？以及是否所有人在做这个实验时，结果都是一样的？
我们首先查看在10.0.123.0/24网段，OSPF邻居关系中DR和BDR选举的情况。从下面的输出中，我们可以得知现在该网段的DR的接口IP为10.0.123.1，BDR的接口IP为10.0.123.2。
[R1]display ospf peer
OSPF Process 1 with Router ID 10.0.1.1
Neighbors
Area 0.0.0.0 interface 10.0.123.1(GigabitEthernet0/0/0)'s neighbors
Router ID: 10.0.2.2 Address: 10.0.123.2
State: Full Mode:Nbr is Master Priority: 1
DR: 10.0.123.1 BDR: 10.0.123.2 MTU: 0
Dead timer due in 40 sec
Retrans timer interval: 5
Neighbor is up for 01:03:35
Authentication Sequence: [ 0 ]
Router ID: 10.0.3.3 Address: 10.0.123.3
State: Full Mode:Nbr is Master Priority: 1
DR: 10.0.123.1 BDR: 10.0.123.2 MTU: 0
Dead timer due in 33 sec
Retrans timer interval: 5
Neighbor is up for 01:02:27
Authentication Sequence: [ 0 ]
有可能每个人的实验结果输出不一样。因为在OSPF中，DR的选举不是抢占的，即网络中存在DR或BDR时，新进入网络的路由器不能抢占DR或BDR的角色。在这个网络中，先启动OSPF进程或先接入该网络的路由器成为了该网段上的DR，其他路由器成为的BDR或DROther。
当DR发生故障后，BDR就会接替DR的位置，我们在实验中可以通过重置OSPF进程的方法来观察DR角色的改变，在这里，我们重置R1的OSPF进程。
<R1>reset ospf process
Warning: The OSPF process will be reset. Continue? [Y/N]:y
[R1]display ospf peer
OSPF Process 1 with Router ID 10.0.1.1
Neighbors
Area 0.0.0.0 interface 10.0.123.1(GigabitEthernet0/0/0)'s neighbors
Router ID: 10.0.2.2 Address: 10.0.123.2
State: Full Mode:Nbr is Master Priority: 1
DR: 10.0.123.2 BDR: 10.0.123.3 MTU: 0
Dead timer due in 34 sec
Retrans timer interval: 0
Neighbor is up for 00:00:19
Authentication Sequence: [ 0 ]
Router ID: 10.0.3.3 Address: 10.0.123.3
State: Full Mode:Nbr is Master Priority: 1
DR: 10.0.123.2 BDR: 10.0.123.3 MTU: 0
Dead timer due in 39 sec
Retrans timer interval: 5
Neighbor is up for 00:00:19
Authentication Sequence: [ 0 ]
当重置R1的OSPF进程以后，原来该网络上的BDR 10.0.123.2成为了新的DR，原来的DROther 10.0.123.3成为了新的BDR。
下面我们关闭R1、R2与R3的G0/0/0接口，使用命令debugging ospf 1 event准备查看OSPF邻接关系建立的具体过程。然后尽量同时打开R1、R2与R3的G0/0/0接口。观察在广播式多路访问网络上邻居状态的变化过程和DR和BDR选举的过程。
<R1>debugging ospf 1 event
<R1>terminal debugging
[R1]interface GigabitEthernet 0/0/0
[R1-GigabitEthernet0/0/0]shut
[R1-GigabitEthernet0/0/0]undo shut
<R2>debugging ospf 1 event
<R2>terminal debugging
[R2]interface GigabitEthernet 0/0/0
[R2-GigabitEthernet0/0/0]shut
[R2-GigabitEthernet0/0/0]undo shut
<R3>debugging ospf 1 event
<R3>terminal debugging
[R3]interface GigabitEthernet 0/0/0
[R3-GigabitEthernet0/0/0]shutdown
[R3-GigabitEthernet0/0/0]undo shutdown
在R2和R3上进行相同的操作，查看R3的debug信息。由于所有路由器默认的接口优先级都是1，所以在DR选举的时候会参考路由器的Router ID，在这三台路由器中，R3的Router ID是最大的，所以R3成为了该网段上的DR。
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:54:59.220.1+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802c Line: 1326 Level: 0x20
OSPF 1: Intf 10.0.123.3 Rcv InterfaceUp State Down -> Waiting.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:54:59.230.1+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802c Line: 1440 Level: 0x20
OSPF 1 Send Hello Interface Up on 10.0.123.3
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:08.550.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1200 Level: 0x20
OSPF 1: Nbr 10.0.123.1 Rcv HelloReceived State Down -> Init.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:09.530.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1200 Level: 0x20
OSPF 1: Nbr 10.0.123.2 Rcv HelloReceived State Down -> Init.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:18.540.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1796 Level: 0x20
OSPF 1: Nbr 10.0.123.1 Rcv 2WayReceived State Init -> 2Way.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:19.570.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1796 Level: 0x20
OSPF 1: Nbr 10.0.123.2 Rcv 2WayReceived State Init -> 2Way.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.370.1+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1796 Level: 0x20
OSPF 1: Nbr 10.0.123.1 Rcv AdjOk? State 2Way -> ExStart.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.370.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1796 Level: 0x20
OSPF 1: Nbr 10.0.123.2 Rcv AdjOk? State 2Way -> ExStart.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.370.3+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802c Line: 2127 Level: 0x20
OSPF 1 Send Hello Interface State Changed on 10.0.123.3
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.370.4+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802c Line: 2138 Level: 0x20
OSPF 1: Intf 10.0.123.3 Rcv WaitTimer State Waiting -> DR.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.390.1+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1909 Level: 0x20
OSPF 1: Nbr 10.0.123.1 Rcv NegotiationDone State ExStart -> Exchange.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.390.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1909 Level: 0x20
OSPF 1: Nbr 10.0.123.2 Rcv NegotiationDone State ExStart -> Exchange.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.400.1+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 2021 Level: 0x20
OSPF 1: Nbr 10.0.123.1 Rcv ExchangeDone State Exchange -> Loading.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.400.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 2423 Level: 0x20
OSPF 1: Nbr 10.0.123.1 Rcv LoadingDone State Loading -> Full.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.400.3+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 2021 Level: 0x20
OSPF 1: Nbr 10.0.123.2 Rcv ExchangeDone State Exchange -> Loading.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.400.4+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 2423 Level: 0x20
OSPF 1: Nbr 10.0.123.2 Rcv LoadingDone State Loading -> Full.
<R1>undo debugging all
<R2>undo debugging all
<R3>undo debugging all
当刚打开接口时，接口状态由Down变为Waiting，此时路由器开始交互Hello数据包，等待约40秒以后，R3的接口由Waiting变为DR。
步骤四.配置OSPF中Loopback接口的网络类型
观察R1的路由表，关注这两条路由：10.0.2.2/32和10.0.3.3/32。
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.2.2/32 OSPF 10 1 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.3/32 OSPF 10 1 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
在配置R2和R3的Loopback接口地址时，使用的掩码是24位，分析为什么这里路由表中显示的是32位掩码的路由？
使用命令display ospf interface LoopBack 0 verbose查看OSPF在Loopback 0接口运行的状态信息。
[R1]display ospf interface LoopBack 0 verbose
OSPF Process 1 with Router ID 10.0.1.1
Interfaces
Interface: 10.0.1.1 (LoopBack0)
Cost: 0 State: P-2-P Type: P2P MTU: 1500
Timers: Hello 10 , Dead 40 , Poll 120 , Retransmit 5 , Transmit Delay 1
IO Statistics
Type Input Output
Hello 0 0
DB Description 0 0
Link-State Req 0 0
Link-State Update 0 0
Link-State Ack 0 0
ALLSPF GROUP
OpaqueId: 0 PrevState: Down
可以看到对于Loopback接口，OSPF知道该网段只可能有一个IP地址，所以发布的路由的子网掩码是32位的。
修改R2的Loopback0接口的网络类型为Broadcast，OSPF在发布这个接口的网络信息时，就会使用24位掩码进行发布。
[R2]interface LoopBack 0
[R2-LoopBack0]ospf network-type broadcast
这时我们看到R2发布的Loopback 0地址的路由子网掩码为24位。
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.2.2/24 OSPF 10 1 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.3/32 OSPF 10 1 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
使用命令display ospf interface LoopBack 0 verbose查看Loopback接口的运行状态可以看到，该接口网络类型为Broadcast。
[R2]display ospf interface LoopBack 0 verbose
OSPF Process 1 with Router ID 10.0.2.2
Interfaces
Interface: 10.0.2.2 (LoopBack0)
Cost: 0 State: DR Type: Broadcast MTU: 1500
Priority: 1
Designated Router: 10.0.2.2
Backup Designated Router: 0.0.0.0
Timers: Hello 10 , Dead 40 , Poll 120 , Retransmit 5 , Transmit Delay 1
IO Statistics
Type Input Output
Hello 0 0
DB Description 0 0
Link-State Req 0 0
Link-State Update 0 0
Link-State Ack 0 0
ALLSPF GROUP
ALLDR GROUP
OpaqueId: 0 PrevState: Waiting
步骤五.修改接口的OSPF代价值
首先在R1上查看R1到达R3的Loopback0接口路由的代价值，我们可以看到到达10.0.3.3/32的代价值为1。
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.2.2/24 OSPF 10 1 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.3/32 OSPF 10 1 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
修改R1的G0/0/0接口代价值为20，修改R3的G0/0/0接口代价值为10。
[R1]interface GigabitEthernet 0/0/0
[R1-GigabitEthernet0/0/0]ospf cost 20
[R1-GigabitEthernet0/0/0]quit
[R3]interface GigabitEthernet 0/0/0
[R3-GigabitEthernet0/0/0]ospf cost 10
[R3-GigabitEthernet0/0/0]quit
重新查看R1到达R3的Loopback0接口路由的代价值，可以看到，到达10.0.3.3/32的代价值为20。
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.2.2/24 OSPF 10 20 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.3/32 OSPF 10 20 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
在R3上查看10.0.1.1/32的代价值，可以看到值为10。
[R3]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.1/32 OSPF 10 10 D 10.0.123.1 GigabitEthernet0/0/0
10.0.2.0/24 OSPF 10 10 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.0/24 Direct 0 0 D 10.0.3.3 LoopBack0
10.0.3.3/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.3.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.123.0/24 Direct 0 0 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.3/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
步骤六.配置OSPF的Silent-interface
配置R1的G0/0/0接口为Silent-interface。
[R1]ospf 1
[R1-ospf-1]silent-interface GigabitEthernet 0/0/0
[R1-ospf-1]quit
查看R1的邻居关系建立和路由表学习情况可发现，路由表中从OSPF学习到的路由条目消失了。
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
查看R1的邻居列表可以看到R1和R2、R3之间的邻居关系也消失了。在RIP中将一个接口置为Silent-interface以后，该接口不再发送RIP更新；但在OSPF中，路由器之间需要建立邻居关系之后才会交互路由信息，当一个接口被设置为Silent-interface以后，该接口不再接收或发送Hello包，造成该接口不能和其他路由器形成邻居关系。
[R1]display ospf interface GigabitEthernet 0/0/0
OSPF Process 1 with Router ID 10.0.1.1
Interfaces
Interface: 10.0.123.1 (GigabitEthernet0/0/0)
Cost: 20 State: DR Type: Broadcast MTU: 1500
Priority: 1
Designated Router: 10.0.123.1
Backup Designated Router: 0.0.0.0
Timers: Hello 10 , Dead 40 , Poll 120 , Retransmit 5 , Transmit Delay 1
Silent interface, No hellos
恢复R1的G0/0/0接口为默认状态，将三个路由器的Loopback0接口配置为Silent-interface。
[R1]ospf 1
[R1-ospf-1]undo silent-interface GigabitEthernet0/0/0
[R1-ospf-1]silent-interface LoopBack 0
[R1-ospf-1]quit
[R2]ospf 1
[R2-ospf-1]silent-interface LoopBack 0
[R1-ospf-1]quit
[R3]ospf 1
[R3-ospf-1]silent-interface LoopBack 0
[R1-ospf-1]quit
检查R1的路由表可见，将Loopback设为Silent-interface以后不影响该接口路由的发布。
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.2.0/24 OSPF 10 20 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.3/32 OSPF 10 20 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
附加实验: 思考并验证
为什么在配置OSPF时，使用的通配符掩码是0.0.0.0，实际的配置中，也可以使用通配符掩码0.0.0.255，思考一下，这两种表达形式有什么差异？
分析在实际的网络中，哪些类型的接口应该配置为Silent-interface接口？
最终设备配置
<R1>display current-configuration
[V200R007C00SPC600]
#
sysname R1
#
interface GigabitEthernet0/0/0
ip address 10.0.123.1 255.255.255.0
ospf cost 20
#
interface LoopBack0
ip address 10.0.1.1 255.255.255.0
#
ospf 1 router-id 10.0.1.1
silent-interface LoopBack0
area 0.0.0.0
authentication-mode simple plain huawei
network 10.0.1.1 0.0.0.0
network 10.0.123.1 0.0.0.0
#
return
<R2>display current-configuration
[V200R007C00SPC600]
#
sysname R2
#
interface GigabitEthernet0/0/0
ip address 10.0.123.2 255.255.255.0
#
interface LoopBack0
ip address 10.0.2.2 255.255.255.0
ospf network-type broadcast
#
ospf 1 router-id 10.0.2.2
silent-interface LoopBack0
area 0.0.0.0
authentication-mode simple plain huawei
network 10.0.2.2 0.0.0.0
network 10.0.123.2 0.0.0.0
#
return
<R3>display current-configuration
[V200R007C00SPC600]
#
sysname R3
#
interface GigabitEthernet0/0/0
ip address 10.0.123.3 255.255.255.0
ospf cost 10
#
interface LoopBack0
ip address 10.0.3.3 255.255.255.0
#
ospf 1 router-id 10.0.3.3
silent-interface LoopBack0
area 0.0.0.0
authentication-mode simple plain huawei
network 10.0.3.3 0.0.0.0
network 10.0.123.3 0.0.0.0
#
return