OSPF特殊区域之STUB

最新推荐文章于 2025-05-10 10:04:25 发布

cmdsystem

最新推荐文章于 2025-05-10 10:04:25 发布

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分类专栏：网络之路文章标签： OSPF

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本文探讨了OSPF划分区域的优势，重点解析了Stub区域的特点，包括其不接受4、5类路由，不允许ASBR存在等。通过实验拓扑，展示了配置Stub区域并观察路由情况的过程，同时提及了如何将Stub区域转换为Totally Stub区域以避免外部路由的lsa3。此外，还提到了在有多个ABR时调整cost值以优化选路的方法。

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OSPF划分区域优点：
减小LSDB（lsa泛洪），同时保证到达目标网络的可达性
减小路由震荡
stub（末节网络）区域特点
1. 一个区域配置为stub时，所有相关路由器都需要配置该属性
2. 如果stub区域边界有多个ABR时，注意选路（修改cost）
3. 该区域不接受4、5类路由
4. 不能出现ASBR
5. 不能为区域0
6. 虚连接不能出现在该区域
7. ABR会自动下发一条缺省路由
实验拓扑

需求
1. A1配置为stub区域，查看到R5的路由情况（在R3的ospf进程中引入rip路由）
2. 查看各个区域都存在几类路由
3. R1、R2的loopback发布在0区，R3的loopback发布在2区，R5的loopback发布在rip中
完成ip网络基本配置，以及ospf邻居建立，查看邻居情况如下：

#R1
<R1>dis ospf peer brief 

         OSPF Process 1 with Router ID 1.1.1.1
                  Peer Statistic Information
 ----------------------------------------------------------------------------
 Area Id          Interface                        Neighbor id      State    
 0.0.0.0          Serial0/0/1                      2.2.2.2          Full        
 0.0.0.2          Serial0/0/0                      3.3.3.3          Full        
 ----------------------------------------------------------------------------
<R1>

#R2
<R2>dis ospf peer brief 

         OSPF Process 1 with Router ID 2.2.2.2
                  Peer Statistic Information
 ----------------------------------------------------------------------------
 Area Id          Interface                        Neighbor id      State    
 0.0.0.0          Serial0/0/0                      1.1.1.1          Full        
 0.0.0.1          Serial0/0/1                      4.4.4.4          Full        
 ----------------------------------------------------------------------------
<R2>

#R3
<R3>dis ospf peer brief 

         OSPF Process 1 with Router ID 3.3.3.3
                  Peer Statistic Information
 ----------------------------------------------------------------------------
 Area Id          Interface                        Neighbor id      State    
 0.0.0.2          Serial0/0/0                      1.1.1.1          Full        
 ----------------------------------------------------------------------------
<R3>

#R4
<R4>dis ospf peer brief 

         OSPF Process 1 with Router ID 4.4.4.4
                  Peer Statistic Information
 ----------------------------------------------------------------------------
 Area Id          Interface                        Neighbor id      State    
 0.0.0.1          Serial0/0/1                      2.2.2.2          Full        
 ----------------------------------------------------------------------------
<R4>
ospf邻居建立正常

#查看R3是否学到R5的loopback
<R3>dis ip routing-table  p rip 
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Public routing table : RIP
         Destinations : 1        Routes : 1        

RIP routing table status : <Active>
         Destinations : 1        Routes : 1

Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

       51.1.1.0/24  RIP     100  1           D   35.1.1.5        Serial0/0/1

RIP routing table status : <Inactive>
         Destinations : 0        Routes : 0

<R3>

R3已学到R5的loopback路由，直接到最左侧R4上查看路由情况
<R4>dis ospf lsdb 

         OSPF Process 1 with Router ID 4.4.4.4
                 Link State Database 

                         Area: 0.0.0.1
 Type      LinkState ID    AdvRouter          Age  Len   Sequence   Metric
 Router    4.4.4.4         4.4.4.4            701  60    80000004    1562
 Router    2.2.2.2         2.2.2.2            702  48    80000003    1562
 Sum-Net   21.1.1.1        2.2.2.2            712  28    80000002       0
 Sum-Net   12.1.1.0        2.2.2.2            712  28    80000002    1562
 Sum-Net   11.1.1.1        2.2.2.2            712  28    80000002    1562
 Sum-Net   31.1.1.1        2.2.2.2            712  28    80000002    3124
 Sum-Net   13.1.1.0        2.2.2.2            712  28    80000002    3124
 Sum-Asbr  3.3.3.3         2.2.2.2            712  28    80000002    3124


                 AS External Database
 Type      LinkState ID    AdvRouter          Age  Len   Sequence   Metric
 External  51.1.1.0        3.3.3.3            698  36    80000002       1
 External  35.1.1.0        3.3.3.3            700  36    80000002       1

<R4>
可以看到已经学到R5的外部路由，R4上存在1、3、4、5类lsa（lsa2存在于MA网络）
注意此处的External路由的cost，在R3的ospf上引入rip时需要注意type1、type2的区别
*type1，经过的路径会累加cost值，可以反映出路径的花销
*type2，经过的路径不会累加cost值
-----------------------华丽的分割线-----------------------
配置A1区域为stub区域
将R4的A1区域配置为stb后，此时邻居会中断（在hello中区域flag必须一致），将R2的A1区域也配置为stub后，此时邻居建立
[R4-ospf-1-area-0.0.0.1]stub 
[R4-ospf-1-area-0.0.0.1]
Aug 28 2015 00:08:04-08:00 R4 %%01OSPF/3/NBR_CHG_DOWN(l)[0]:Neighbor event:neighbor state changed to Down. (ProcessId=1, NeighborAddress=2.2.2.2, NeighborEvent=KillNbr, NeighborPreviousState=Full, NeighborCurrentState=Down)
Aug 28 2015 00:08:04-08:00 R4 %%01OSPF/3/NBR_DOWN_REASON(l)[1]:Neighbor state leaves full or changed to Down. (ProcessId=1, NeighborRouterId=2.2.2.2, NeighborAreaId=1, NeighborInterface=Serial0/0/1,NeighborDownImmediate reason=Neighbor Down Due to Kill Neighbor, NeighborDownPrimeReason=Area reset, NeighborChangeTime=2015-08-28 00:08:04-08:00)
[R4-ospf-1-area-0.0.0.1]
Aug 28 2015 00:08:13-08:00 R4 DS/4/DATASYNC_CFGCHANGE:OID 1.3.6.1.4.1.2011.5.25.191.3.1 configurations have been changed. The current change number is 19, the change loop count is 0, and the maximum number of records is 4095.
Aug 28 2015 00:08:15-08:00 R4 %%01OSPF/4/NBR_CHANGE_E(l)[2]:Neighbor changes event: neighbor status changed. (ProcessId=1, NeighborAddress=24.1.1.2, NeighborEvent=HelloReceived, NeighborPreviousState=Down, NeighborCurrentState=Init)
Aug 28 2015 00:08:25-08:00 R4 %%01OSPF/4/NBR_CHANGE_E(l)[3]:Neighbor changes event: neighbor status changed. (ProcessId=1, NeighborAddress=24.1.1.2, NeighborEvent=2WayReceived, NeighborPreviousState=Init, NeighborCurrentState=ExStart)
Aug 28 2015 00:08:25-08:00 R4 %%01OSPF/4/NBR_CHANGE_E(l)[4]:Neighbor changes event: neighbor status changed. (ProcessId=1, NeighborAddress=24.1.1.2, NeighborEvent=NegotiationDone, NeighborPreviousState=ExStart, NeighborCurrentState=Exchange)
Aug 28 2015 00:08:25-08:00 R4 %%01OSPF/4/NBR_CHANGE_E(l)[5]:Neighbor changes event: neighbor status changed. (ProcessId=1, NeighborAddress=24.1.1.2, NeighborEvent=ExchangeDone, NeighborPreviousState=Exchange, NeighborCurrentState=Loading)
Aug 28 2015 00:08:25-08:00 R4 %%01OSPF/4/NBR_CHANGE_E(l)[6]:Neighbor changes event: neighbor status changed. (ProcessId=1, NeighborAddress=24.1.1.2, NeighborEvent=LoadingDone, NeighborPreviousState=Loading, NeighborCurrentState=Full)
[R4-ospf-1-area-0.0.0.1]

邻居建立后再次查看路由、lsa情况
[R4]dis ip routing-tabl p o
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Public routing table : OSPF
         Destinations : 6        Routes : 6        

OSPF routing table status : <Active>
         Destinations : 6        Routes : 6

Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface

        0.0.0.0/0   OSPF    10   1563        D   24.1.1.2        Serial0/0/1
       11.1.1.1/32  OSPF    10   3124        D   24.1.1.2        Serial0/0/1
       12.1.1.0/24  OSPF    10   3124        D   24.1.1.2        Serial0/0/1
       13.1.1.0/24  OSPF    10   4686        D   24.1.1.2        Serial0/0/1
       21.1.1.1/32  OSPF    10   1562        D   24.1.1.2        Serial0/0/1
       31.1.1.1/32  OSPF    10   4686        D   24.1.1.2        Serial0/0/1

OSPF routing table status : <Inactive>
         Destinations : 0        Routes : 0

[R4]
已经不存在外部路由，同时会下发一条缺省路由

查看lsa
[R4]dis ospf lsdb 

         OSPF Process 1 with Router ID 4.4.4.4
                 Link State Database 

                         Area: 0.0.0.1
 Type      LinkState ID    AdvRouter          Age  Len   Sequence   Metric
 Router    4.4.4.4         4.4.4.4            231  60    80000003    1562
 Router    2.2.2.2         2.2.2.2            232  48    80000003    1562
 Sum-Net   0.0.0.0         2.2.2.2            242  28    80000001       1
 Sum-Net   21.1.1.1        2.2.2.2            242  28    80000001       0
 Sum-Net   12.1.1.0        2.2.2.2            242  28    80000001    1562
 Sum-Net   11.1.1.1        2.2.2.2            242  28    80000001    1562
 Sum-Net   31.1.1.1        2.2.2.2            242  28    80000001    3124
 Sum-Net   13.1.1.0        2.2.2.2            242  28    80000001    3124

[R4]
此时只存在1、3类lsa