ospf故障分析案例.docx

1、ospf故障分析案例资料编码产品名称使用对象产品版本编写部门资料版本Ospf故障分析拟 制：日 期：审 核：日 期：审 核：日 期：批 准：日 期：华 为 技 术 有 限 公 司版权所有 XX修订记录日期修订版本描述作者2009-9-191.0初稿杨明祥 目 录第1章 场景描述 51.1 场景描述 5第2章 故障分析 62.1 故障分析 62.1.1 SW2与SW4间接口为广播类型 62.1.2 SW2与SW4间接口为点到点类型 62.2 故障前后信息分析 72.2.1 链路正常时，从SW2看自己产生的router lsa 72.2.2 链路正常时，从SW4看自己生成的lsa 82.2.3 链

2、路故障后，从SW2看自己产生的router lsa 102.2.4 链路故障后，从SW4看自己产生的router lsa 112.2.5 链路故障后，SW4等到dead超时后信息 13关键词：Ospf、故障、收敛、SPF运算、CISCO交换机摘 要：本文以4台CISCO 3550交换机组网，分析小型网络中，出现故障时，OSPF的收敛过程。第1章 场景描述1.1 场景描述如下图，4台设备为CISCO 3550交换机。SW3工作在二层，其它三个SW工作在三层，运行在OSPF area 0。SW2和SW4网段上，SW4为DR。正常情况从SW2到4.4.4.4的往返流量都从SW3走。第2章 故障分析2

3、.1 故障分析2.1.1 SW2与SW4间接口为广播类型 从SW2一直ping 4.4.4.4，断开SW2的F0/24，看网络收敛时间。1) 链路正常时，SW2产生router lsa包含1.1.24.0/24 网段信息，SW4产生router lsa其中包含1.1.24.0/24 网段信息，且为transit network，同时产生network lsa。2) 当链路故障后，SW4上OSPF dead没有超时前。SW2产生新router lsa,其中没有1.1.24.0/24 网段信息, SW2会很快进行spf运算。3) SW4上产生的lsa信息不变。SW4收到SW2的新lsa,lsdb信

4、息改变，则会重新进行SPF运算。Spf对network lsa运算时，需要检查SW2的router lsa，是否包含1.1.24.0/24 网段信息，如果不包括，说明两端拓扑信息不一致，则不运算此路径。4) 当SW4上OSPF dead超时后。SW4上产生router lsa包含1.1.24.0/24 网段信息，网段信息变为stub network；同时相应的network lsa删除。SW4上ospf dead time超时后，SW4 上router lsa对应的网络类型由transit network变为stub network,同时network lsa删除。LSDB变化，全网设备SPF

5、重新再进行一次运算。2.1.2 SW2与SW4间接口为点到点类型 如果将SW2和SW4的OSPF链路类型改成P2P:从SW2一直ping 4.4.4.4，断开SW2的F0/24，看网络收敛时间。1) 对于Full的邻居来说，router lsa中会有两个描述该网络的router lsa，一个是p2p的，用来描述邻居;一个是stub的，用来描述接口。2) 当sw2和sw3之间链路故障后，sw2发布新的router lsa，由于拔光线或者shutdown接口，那么sw2接口down掉，邻居断开，发布的lsa中就不再有描述该网络的lsa了。SW2很快进行SPF运算。3) sw4收到sw2更新后的ls

6、a，进行路由计算。sw4发布的router lsa中有描述该网络和邻居的lsa。在利用描述该邻居的lsa，即p2p的lsa计算的时候，需要获取sw2发布的router lsa，以检查上面是否有描述sw4这个邻居的p2p的lsa。很显然，没有，所以这条路算不通。4) sw4邻居断开后，重新发布router lsa，里面没有了描述邻居的p2p的lsa，只有描述接口的stub lsa，lsdb变化，全网重新路由计算。2.2 故障前后信息分析2.2.1 链路正常时，从SW2看自己产生的router lsa SW2#show ip ospf dat rout self-originate OSPF Ro

7、uter with ID (2.2.2.2) (Process ID 100) Router Link States (Area 0) LS age: 1296 Options: (No TOS-capability, DC) LS Type: Router Links Link State ID: 2.2.2.2 Advertising Router: 2.2.2.2 LS Seq Number: 80000011 Checksum: 0xB1DF Length: 60 Number of Links: 3 Link connected to: a Transit Network (Link

8、 ID) Designated Router address: 1.1.24.4 (Link Data) Router Interface address: 1.1.24.2 Number of TOS metrics: 0 TOS 0 Metrics: 1 Link connected to: a Transit Network (Link ID) Designated Router address: 1.1.12.2 (Link Data) Router Interface address: 1.1.12.2 Number of TOS metrics: 0 TOS 0 Metrics:

9、1 Link connected to: a Stub Network (Link ID) Network/subnet number: 2.2.2.2 (Link Data) Network Mask: 255.255.255.255 Number of TOS metrics: 0 TOS 0 Metrics: 1 2.2.2 链路正常时，从SW4看自己生成的lsa SW4#show ip ospf database router self-originate OSPF Router with ID (4.4.4.4) (Process ID 100) Router Link States

10、 (Area 0) LS age: 18 Options: (No TOS-capability, DC) LS Type: Router Links Link State ID: 4.4.4.4 Advertising Router: 4.4.4.4 LS Seq Number: 8000001A Checksum: 0xA2C6 Length: 60 Number of Links: 3 Link connected to: a Transit Network (Link ID) Designated Router address: 1.1.24.4 (Link Data) Router

11、Interface address: 1.1.24.4 Number of TOS metrics: 0 TOS 0 Metrics: 1 Link connected to: a Transit Network (Link ID) Designated Router address: 1.1.14.1 (Link Data) Router Interface address: 1.1.14.4 Number of TOS metrics: 0 TOS 0 Metrics: 1 Link connected to: a Stub Network (Link ID) Network/subnet

12、 number: 4.4.4.4 (Link Data) Network Mask: 255.255.255.255 Number of TOS metrics: 0 TOS 0 Metrics: 1 SW4#show ip ospf database network self-originate OSPF Router with ID (4.4.4.4) (Process ID 100) Net Link States (Area 0) Routing Bit Set on this LSA LS age: 23 Options: (No TOS-capability, DC) LS Typ

13、e: Network Links Link State ID: 1.1.24.4 (address of Designated Router) Advertising Router: 4.4.4.4 LS Seq Number: 80000001 Checksum: 0xC92A Length: 32 Network Mask: /24 Attached Router: 4.4.4.4 Attached Router: 2.2.2.2 SW4#show ip ospf nei Neighbor ID Pri State Dead Time Address Interface 2.2.2.2 1

14、 FULL/BDR 00:00:37 1.1.24.2 GigabitEthernet0/24 1.1.1.1 1 FULL/DR 00:00:39 1.1.14.1 GigabitEthernet0/1 2.2.3 链路故障后，从SW4看自己产生的router lsa SW4#show ip ospf database router 2.2.2.2 OSPF Router with ID (4.4.4.4) (Process ID 100) Router Link States (Area 0) LS age: 3 Options: (No TOS-capability, DC) LS Ty

15、pe: Router Links Link State ID: 2.2.2.2 Advertising Router: 2.2.2.2 LS Seq Number: 80000017 Checksum: 0xB81B Length: 48 Number of Links: 2 Link connected to: a Transit Network (Link ID) Designated Router address: 1.1.12.2 (Link Data) Router Interface address: 1.1.12.2 Number of TOS metrics: 0 TOS 0

16、Metrics: 1 Link connected to: a Stub Network (Link ID) Network/subnet number: 2.2.2.2 (Link Data) Network Mask: 255.255.255.255 Number of TOS metrics: 0 TOS 0 Metrics: 1 2.2.4 链路故障后，从SW4看自己产生的router lsa SW4#show ip ospf database router self-originate OSPF Router with ID (4.4.4.4) (Process ID 100) Ro

17、uter Link States (Area 0) LS age: 72 Options: (No TOS-capability, DC) LS Type: Router Links Link State ID: 4.4.4.4 Advertising Router: 4.4.4.4 LS Seq Number: 8000001C Checksum: 0xB2B2 Length: 60 Number of Links: 3 Link connected to: a Transit Network (Link ID) Designated Router address: 1.1.24.4 (Li

18、nk Data) Router Interface address: 1.1.24.4 Number of TOS metrics: 0 TOS 0 Metrics: 1 Link connected to: a Transit Network (Link ID) Designated Router address: 1.1.14.1 (Link Data) Router Interface address: 1.1.14.4 Number of TOS metrics: 0 TOS 0 Metrics: 1 Link connected to: a Stub Network (Link ID

19、) Network/subnet number: 4.4.4.4 (Link Data) Network Mask: 255.255.255.255 Number of TOS metrics: 0 TOS 0 Metrics: 1 SW4#show ip ospf database network self-originate OSPF Router with ID (4.4.4.4) (Process ID 100) Net Link States (Area 0) Routing Bit Set on this LSA LS age: 23 Options: (No TOS-capabi

20、lity, DC) LS Type: Network Links Link State ID: 1.1.24.4 (address of Designated Router) Advertising Router: 4.4.4.4 LS Seq Number: 80000001 Checksum: 0xC92A Length: 32 Network Mask: /24 Attached Router: 4.4.4.4 Attached Router: 2.2.2.2 2.2.5 链路故障后，SW4等到dead超时后信息 SW4#show ip ospf database router self

21、-originate OSPF Router with ID (4.4.4.4) (Process ID 100) Router Link States (Area 0) LS age: 3 Options: (No TOS-capability, DC) LS Type: Router Links Link State ID: 4.4.4.4 Advertising Router: 4.4.4.4 LS Seq Number: 8000001D Checksum: 0xF76 Length: 60 Number of Links: 3 Link connected to: a Stub Ne

22、twork (Link ID) Network/subnet number: 1.1.24.0 (Link Data) Network Mask: 255.255.255.0 Number of TOS metrics: 0 TOS 0 Metrics: 1 Link connected to: a Transit Network (Link ID) Designated Router address: 1.1.14.1 (Link Data) Router Interface address: 1.1.14.4 Number of TOS metrics: 0 TOS 0 Metrics:

23、1 Link connected to: a Stub Network (Link ID) Network/subnet number: 4.4.4.4 (Link Data) Network Mask: 255.255.255.255 Number of TOS metrics: 0 TOS 0 Metrics: 1 SW4# *Mar 1 01:18:54.681: %OSPF-5-ADJCHG: Process 100, Nbr 2.2.2.2 on GigabitEthernet0/24 from FULL to DOWN, Neighbor Down: Dead timer expiredshow ip ospf database network self-originate OSPF Router with ID (4.4.4.4) (Process ID 100) Dead超时后，Network lsa删除。