OSPF故障排除实例分析

  • 发布于:2021-08-04
  • 192 人围观
  实例一 网络类型不一致
  配置如下表所示:
   
  ROUTE1#show ip ospf interface serial 1
  
  Serial1 is up, line protocol is up
  
   Internet Address 10.1.1.1/24, Area 0
  
   Process ID 20, Router ID 10.1.2.1, Network Type BROADCAST, Cost: 64
  
   Transmit Delay is 1 sec, State DR, Priority 1
  
   Designated Router (ID) 10.1.2.1, Interface address 10.1.1.1
  
   Backup Designated router (ID) 10.1.1.2, Interface address 10.1.1.2
  
   Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
  
    Hello due in 00:00:08
  
   Neighbor Count is 1, Adjacent neighbor count is 1
  
    Adjacent with neighbor 10.1.1.2 (Backup Designated Router)
  
   Suppress hello for 0 neighbor(s)
  
  ROUTE2#show ip ospf interface serial 1/1
  
  Serial1/1 is up, line protocol is up
  
   Internet Address 10.1.1.2/24, Area 0
  
   Process ID 20, Router ID 10.1.1.2, Network Type POINT_TO_POINT, Cost: 64
  
   Transmit Delay is 1 sec, State POINT_TO_POINT,
  
   Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
  
    Hello due in 00:00:02
  
   Neighbor Count is 1, Adjacent neighbor count is 1
  
    Adjacent with neighbor 10.1.2.1
  
   Suppress hello for 0 neighbor(s)
  
  从上面可以看出,路由器Router1是配置broadcast模式,而路由器Roure2配置成点对点模块。这种网络类型的不匹配,导致了路由通告的不可达。
  
  ROUTE1#show ip ospf database router 10.1.1.2
  
   Adv Router is not-reachable
  
   LS age: 418
  
   Options: (No TOS-capability, DC)
  
   LS Type: Router Links
  
   Link State ID: 10.1.1.2
  
   Advertising Router: 10.1.1.2
  
   LS Seq Number: 80000002
  
   Checksum: 0xFA63
  
   Length: 60
  
    Number of Links: 3
  
    Link connected to: another Router (point-to-point)
  
    (Link ID) Neighboring Router ID: 10.1.2.1
  
    (Link Data) Router Interface address: 10.1.1.2
  
    Number of TOS metrics: 0
  
    TOS 0 Metrics: 64
  
    Link connected to: a Stub Network
  
    (Link ID) Network/subnet number: 10.1.1.0
  
    (Link Data) Network Mask: 255.255.255.0
  
    Number of TOS metrics: 0
  
    TOS 0 Metrics: 64
  
  ROUTE2#show ip ospf database router 10.1.2.1
  
   Adv Router is not-reachable
  
   LS age: 357
  
   Options: (No TOS-capability, DC)
  
   LS Type: Router Links
  
   Link State ID: 10.1.2.1
  
   Advertising Router: 10.1.2.1
  
   LS Seq Number: 8000000A
  
   Checksum: 0xD4AA
  
   Length: 48
  
    Number of Links: 2
  
     Link connected to: a Transit Network
  
     (Link ID) Designated Router address: 10.1.1.1
  
     (Link Data) Router Interface address: 10.1.1.1
  
     Number of TOS metrics: 0
  
     TOS 0 Metrics: 64
  
  可以看出,对于子网10.1.1.0/24, 路由器ROUTE2产生一个点对点连接,而路由器Router2则产生一个透过的连接,这就在链路状态数据库中产了不一致,从而导致路由信息不会出现在路由表中。
  
  ROUTE2#show ip route
  
  10.1.0.0/16 is variably subnetted, 3 subnets, 2 masks
  
  C    10.1.1.0/24 is directly connected, Serial1/1
  
  C    10.1.3.1/32 is directly connected, Loopback0
  
  解决方案:
  
  为了解决这个问题,需要将两边的网络类型配置为一致。既可以将Router1上的网络类型改为点对点,也可以将Router2上的网络类型改为broadcast.在这个例子中我们将Router1上的网络类型修改为点对点类型。
  
  ROUTE1#configure terminal
  
  ROUTE1(config)#interface serial 1
  
  ROUTE1(config-if)#no ip ospf network broadcast
  
  ROUTE1(config-if)#end
  
  ROUTE1#show ip ospf interface serial 1
  
   Serial1 is up, line protocol is up
  
   Internet Address 10.1.1.1/24, Area 0
  
   Process ID 20, Router ID 10.1.2.1, Network Type POINT_TO_POINT, Cost: 64
  
   Transmit Delay is 1 sec, State POINT_TO_POINT,
  
   Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
  
    Hello due in 00:00:04
  
   Neighbor Count is 1, Adjacent neighbor count is 1
  
   Adjacent with neighbor 10.1.1.2
  
   Suppress hello for 0 neighbor(s)
  
    至此,故障排除。
  
  需要注意的是,如果有一端的接口是多接口,而另一端是子接口,那么需要将两边都修改为broadcast接口。
  
  实例二、一端Unnumbered另一端Numbered
  配置如下表:
  
   ROUTER1#show interface serial 1
  
  Serial1 is up, line protocol is up
  
   Hardware is cxBus Serial
  
   Interface is unnumbered. Using address of Loopback0 (10.1.2.1)
  
  ROUTER2#show interface serial 1/1
  
  Serial1/1 is up, line protocol is up
  
   Hardware is cxBus Serial
  
   Internet address is 10.1.1.2/24
  
  上面的输出显示出ROUTER1的Serial 1接口是个unnumbered 接口,使用Loopback0的地址,而ROUTER2的Serial 1/1则配置有IP地址。
  
  ROUTER1#show ip ospf interface serial 1
  
  Serial1 is up, line protocol is up
  
   Internet Address 0.0.0.0/24, Area 0
  
   Process ID 20, Router ID 10.1.2.1, Network Type POINT_TO_POINT, Cost: 64
  
   Transmit Delay is 1 sec, State POINT_TO_POINT,
  
   Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
  
    Hello due in 00:00:02
  
   Neighbor Count is 1, Adjacent neighbor count is 1
  
    Adjacent with neighbor 10.1.1.2
  
   Suppress hello for 0 neighbor(s)
  
  ROUTER2#show ip ospf interface serial 1/1
  
  Serial1/1 is up, line protocol is up
  
   Internet Address 10.1.1.2/24, Area 0
  
   Process ID 20, Router ID 10.1.1.2, Network Type POINT_TO_POINT, Cost: 64
  
   Transmit Delay is 1 sec, State POINT_TO_POINT,
  
   Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
  
    Hello due in 00:00:02
  
   Neighbor Count is 1, Adjacent neighbor count is 1
  
    Adjacent with neighbor 10.1.2.1
  
   Suppress hello for 0 neighbor(s)
  
  从上面可以看出,两边的网络类型都是点对点的,出现问题的原因是一边是unnumbered 而另一边则配置有IP地址,这就造成了OSPF数据库中的不一致。
  
  ROUTER1#show ip ospf database router 10.1.1.2
  
   Adv Router is not-reachable
  
   LS age: 418
  
   Options: (No TOS-capability, DC)
  
   LS Type: Router Links
  
   Link State ID: 10.1.1.2
  
   Advertising Router: 10.1.1.2
  
   LS Seq Number: 80000002
  
   Checksum: 0xFA63
  
   Length: 60
  
    Number of Links: 3
  
    Link connected to: another Router (point-to-point)
  
    (Link ID) Neighboring Router ID: 10.1.2.1
  
    (Link Data) Router Interface address: 10.1.1.2
  
    Number of TOS metrics: 0
  
    TOS 0 Metrics: 64
  
  ROUTER2#show ip ospf database router 10.1.2.1
  
   Adv Router is not-reachable
  
   LS age: 357
  
   Options: (No TOS-capability, DC)
  
   LS Type: Router Links
  
   Link State ID: 10.1.2.1
  
   Advertising Router: 10.1.2.1
  
   LS Seq Number: 8000000A
  
   Checksum: 0xD4AA
  
   Length: 48
  
    Number of Links: 2
  
    Link connected to: another Router (point-to-point)
  
    (Link ID) Neighboring Router ID: 10.1.1.2
  
    (Link Data) Router Interface address: 0.0.0.4
  
    Number of TOS metrics: 0
  
    TOS 0 Metrics: 64
  
  可以看见ROUTER1为这个点到点链路产生了一个包括它的接口地址信息的LSA,而Router2同样产生了一个包括IfIndex值的LSA,这就在链路状态数据库中产生了不一致,也就意味着路由信息不会在路由表中出现。从以下的命令可以看到:
  
  ROUTER2#show ip route
  
  10.1.0.0/16 is variably subnetted, 3 subnets, 2 masks
  
  C    10.1.1.0/24 is directly connected, Serial1/1
  
  C    10.1.3.1/32 is directly connected, Loopback0
  
  解决办法:
  
  要解决这个问题,可以将两边路由器都楝配为unnumbered的,或者为两连路由器的接口都配置上IP地址。在这个例子中我们把Router1的serial1口配置上IP地址。
  
  ROUTER1#configure terminal
  
  ROUTER1(config)#interface serial 1
  
  ROUTER1(config-if)#no ip unnumbered loopback 0
  
  ROUTER1(config-if)#ip address 10.1.1.1 255.255.255.0
  
  ROUTER1)#show ip ospf interface serial 1
  
  Serial1 is up, line protocol is up
  
   Internet Address 10.1.1.1/24, Area 0
  
   Process ID 20, Router ID 10.1.2.1, Network Type POINT_TO_POINT, Cost: 64
  
   Transmit Delay is 1 sec, State POINT_TO_POINT,
  
   Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
  
    Hello due in 00:00:02
  
   Neighbor Count is 1, Adjacent neighbor count is 1
  
    Adjacent with neighbor 10.1.1.2
  
   Suppress hello for 0 neighbor(s)
  
  ROUTER2#show ip route
  
  10.1.0.0/16 is variably subnetted, 3 subnets, 2 masks
  
  C    10.1.1.0/24 is directly connected, Serial1/1
  
  O    10.1.2.1/32 [110/65] via 10.1.1.1, 00:03:08, Serial1/1
  
  C    10.1.3.1/32 is directly connected, Loopback0
  
  至此,问题解决。
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