疑難排解開放最短路徑優先路由資料庫相關問題

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已更新: 2023 年 8 月 28 日
文件 ID:7112

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    簡介

    本文說明當資料庫中的路由不在路由資訊庫 (RIB) 或路由表中時，如何修復 OSPF 問題。

      

    必要條件

    需求

    本文檔的讀者必須瞭解以下主題：

    • 開放最短路徑優先(OSPF)協定的基本知識

    • Cisco IOS®中的OSPF配置基礎知識

    採用元件

    本文中的資訊係根據以下軟體和硬體版本：

    • Cisco IOS軟體版本12及更新版本

    • 所有思科路由器平台都支援此功能

    本文中的資訊是根據特定實驗室環境內的裝置所建立。文中使用到的所有裝置皆從已清除（預設）的組態來啟動。如果您的網路運作中，請確保您瞭解任何指令可能造成的影響。

    慣例

    如需文件慣例的詳細資訊，請參閱思科技術提示慣例。

    背景資訊

    本文描述開放最短路徑優先(OSPF)的一個常見問題，即資料庫中的路由不會出現在路由資訊庫(RIB)或路由表中。在大多數情況下，OSPF會發現資料庫中的差異，因此不會在路由表中安裝路由。通常，當發生此問題時，您會在資料庫的鏈路狀態通告(LSA)上看到Adv Router is not-reachable消息（這意味著通告LSA的路由器無法通過OSPF到達）。以下是範例：

    Router#show ip ospf database router 172.16.32.2

    Adv Router is not-reachable     LS age: 418
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 172.16.32.2
Advertising Router: 172.16.32.2
LS Seq Number: 80000002
Checksum: 0xFA63
Length: 60
 Number of Links: 3

    造成此問題的原因有多種，其中大多數的原因都是配置錯誤或拓撲斷開。更正配置後，OSPF資料庫差異消失，路由顯示在路由表中。本文檔解釋了可能導致資料庫中存在差異的一些更常見原因。

    本文檔中用於驗證OSPF行為的一些命令包括show ip ospf interface、show ip ospf database router、show ip ospf neighbor和show ip ospf database external。如果您的Cisco裝置輸出了這些命令中的任意一個，則可以使用Cisco CLI Analyzer顯示潛在的問題和解決方法。

    原因1：網路型別不匹配

    下一個網路圖用作示例：

    Type Mismatch

    R4-4K

    R1-7010

    		 
    interface Loopback0
 ip address 172.16.33.1 255.255.255.255
!
interface Serial2
 ip address 172.16.32.1 255.255.255.0
 ip ospf network broadcast
!
router ospf 20
 network 172.16.0.0 0.0.255.255 area 0
    		 
    interface Loopback0
 ip address 172.16.30.1 255.255.255.255
!
interface Serial1/0
 ip address 172.16.32.2 255.255.255.0
 clockrate 64000
!
router ospf 20
 network 172.16.0.0 0.0.255.255 area 0
    		 
    R4-4K(4)#show ip ospf interface serial 2
Serial2 is up, line protocol is up 
  Internet Address 172.16.32.1/24, Area 0 
  Process ID 20, Router ID 172.16.33.1, Network Type BROADCAST, Cost: 64
  Transmit Delay is 1 sec, State DR, Priority 1 
  Designated Router (ID) 172.16.33.1, Interface address 172.16.32.1
  Backup Designated router (ID) 172.16.32.2, Interface address 172.16.32.2
  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 172.16.32.2  (Backup Designated Router)
  Suppress hello for 0 neighbor(s)

R1-7010(5)#show ip ospf interface serial 1/0
Serial1/0 is up, line protocol is up 
  Internet Address 172.16.32.2/24, Area 0 
  Process ID 20, Router ID 172.16.32.2, 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 172.16.33.1
  Suppress hello for 0 neighbor(s)

    如前面的輸出所示，路由器R4-4K配置為廣播，路由器R1-7010配置為點對點。這種網路型別不相符會導致廣告路由器無法連線。

    R4-4K(4)#show ip ospf database router 172.16.32.2

  Adv Router is not-reachable
  LS age: 418
  Options: (No TOS-capability, DC)
  LS Type: Router Links
  Link State ID: 172.16.32.2
  Advertising Router: 172.16.32.2
  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: 172.16.33.1
    (Link Data) Router Interface address: 172.16.32.2
    Number of TOS metrics: 0
    TOS 0 Metrics: 64

    Link connected to: a Stub Network
    (Link ID) Network/subnet number: 172.16.32.0
    (Link Data) Network Mask: 255.255.255.0
    Number of TOS metrics: 0
    TOS 0 Metrics: 64

R1-7010(5)#show ip ospf database router 172.16.33.1

  Adv Router is not-reachable
  LS age: 357
  Options: (No TOS-capability, DC)
  LS Type: Router Links
  Link State ID: 172.16.33.1
  Advertising Router: 172.16.33.1
  LS Seq Number: 8000000A
  Checksum: 0xD4AA
  Length: 48
   Number of Links: 2

     Link connected to: a Transit Network
     (Link ID) Designated Router address: 172.16.32.1
     (Link Data) Router Interface address: 172.16.32.1
     Number of TOS metrics: 0
     TOS 0 Metrics: 64

    您可以看到，對於子網172.16.32.0/24，路由器R1-7010生成一條點對點鏈路，路由器R4-4K生成一條傳輸鏈路。這會導致鏈路狀態資料庫中存在不一致，這意味著路由表中未安裝任何路由。

    R1-7010(5)#show ip route
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C       172.16.32.0/24 is directly connected, Serial1/0
C       172.16.30.1/32 is directly connected, Loopback0

    解決方案

    要解決此問題，請將兩台路由器配置為同一網路型別。您可以將路由器R1-7010的網路型別更改為廣播，或者將路由器R4-4K串列介面更改為點對點。

    註：如果出現一端是多點介面而另一端是子介面的情況，請將網路型別更改為兩端廣播。

    在本示例中，我們刪除了R4-4K上的network-type broadcast語句，因為兩端都是點對點高級資料鏈路控制(HDLC)封裝的介面。

    R4-4K(4)#configure terminal 
R4-4K(4)(config)#interface serial 2 
R4-4K(4)(config-if)#no ip ospf network broadcast 
R4-4K(4)(config-if)#end

R4-4K(4)#show ip ospf interface serial 2
 Serial2 is up, line protocol is up 
  Internet Address 172.16.32.1/24, Area 0 
  Process ID 20, Router ID 172.16.33.1, 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 172.16.32.2
  Suppress hello for 0 neighbor(s)

    原因2：雙串列鏈路設定中的地址分配錯誤

    請考慮以下網路圖作為範例：

    Wrong Address Assignment in Dural Serial Link

    R4-4K

    R1-7010

    		 
    interface loopback 0
 ip address 172.16.35.1 255.255.255.255
!
interface Serial2
 ip address 172.16.29.1 255.255.255.0
!
interface Serial3
 ip address 172.16.32.1 255.255.255.0
!
router ospf 20
 network 172.16.0.0 0.0.255.255 area 0
    		 
    interface loopback 0
 ip address 172.16.30.1 255.255.255.255
!
interface Serial1/0
 ip address 172.16.32.2 255.255.255.0
 clockrate 64000
!
interface Serial1/1
 ip address 172.16.29.2 255.255.255.0
 clockrate 38400
!
router ospf 20
 network 172.16.0.0 0.0.255.255 area 0

    您可以看到，IP地址在以前的配置中發生翻轉，導致OSPF資料庫中存在差異。但是，這些路由器仍然在Cisco IOS版本12.1之前形成鄰居，因為在點對點鏈路上，OSPF路由器不會驗證相鄰路由器是否位於同一子網中。

    R4-4K(4)#show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
172.16.32.2       1   FULL/  -        00:00:37    172.16.32.2     Serial2
172.16.32.2       1   FULL/  -        00:00:31    172.16.29.2     Serial3

    從上面的輸出中，您可以看到Serial2用於形成IP地址為172.16.32.2的鄰居，該鄰居不在同一個子網中。雖然形成了鄰居，但路由表中未安裝任何路由：

    R1-7010(5)#show ip route
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C       172.16.32.0/24 is directly connected, Serial1/0
C       172.16.29.0/24 is directly connected, Serial1/1
C       172.16.30.1/32 is directly connected, Loopback0

    解決方案

    要解決此問題，請正確分配IP地址或交換串列電纜。我們已更正以下IP地址：

    R4-4K

    R1-7010

    		 
    interface loopback 0
 ip address 172.16.35.1 255.255.255.255
!
interface Serial2
 ip address 172.16.32.1 255.255.255.0
!
interface Serial3
 ip address 172.16.29.1 255.255.255.0
!
router ospf 20
 network 172.16.0.0 0.0.255.255 area 0
    		 
    interface loopback 0
 ip address 172.16.30.1 255.255.255.255
!
interface Serial1/0
 ip address 172.16.32.2 255.255.255.0
 clockrate 64000
!
interface Serial1/1
 ip address 172.16.29.2 255.255.255.0
 clockrate 38400
!
router ospf 20
 network 172.16.0.0 0.0.255.255 area 0
    		 
    R4-4K(4)#show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
172.16.32.2       1   FULL/  -        00:00:36    172.16.32.2     Serial2
172.16.32.2       1   FULL/  -        00:00:39    172.16.29.2     Serial3

    現在它顯示了Serial 2介面的正確鄰居地址。路由表也包含這些路由：

    R1-7010(5)#show ip route
172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks
C       172.16.32.0/24 is directly connected, Serial1/0
O       172.16.35.1/32 [110/65] via 172.16.32.1, 00:03:12, Serial1/0
                       [110/65] via 172.16.29.1, 00:03:12, Serial1/1
C       172.16.29.0/24 is directly connected, Serial1/1
C       172.16.30.1/32 is directly connected, Loopback0

    原因3：錯誤的主網或子網中包含點對點鏈路的一端

    請考慮以下網路圖作為範例：

    Wrong Majornet or Subnet

    這種情況產生的行為與雙串列鏈路設定中的錯誤地址分配完全相同。要解決此問題，請在兩台路由器上分配同一子網中的IP地址。

    原因4：一側未編號，另一側已編號

    請考慮下一個網路圖作為範例：

    One Side is Numbered

    R4-4K R1-7010 
    interface Loopback0
 ip address 172.16.35.1 255.255.255.255
!
interface Serial2
 ip unnumbered Loopback0
 router ospf 20
 network 172.16.0.0 0.0.255.255 area 0
    		 
    interface Loopback0
 ip address 172.16.30.1 255.255.255.255
!
interface Serial1/0
 ip address 172.16.32.2 255.255.255.0
 clockrate 64000
!
router ospf 20
 network 172.16.0.0 0.0.255.255 area 0
    		 
    R4-4K(4)#show interface serial 2
Serial2 is up, line protocol is up 
  Hardware is cxBus Serial
  Interface is unnumbered.  Using address of Loopback0 (172.16.35.1)

R1-7010(5)#show interface serial 1/0
Serial1/0 is up, line protocol is up 
  Hardware is cxBus Serial
  Internet address is 172.16.32.2/24

    先前的輸出顯示，R4-4K Serial 2介面未編號為Loopback0（使用Loopback0 172.16.35.1的地址），而R1-7010的Serial 1/0介面為編號介面。

    R4-4K(4)#show ip ospf interface serial 2
Serial2 is up, line protocol is up 
  Internet Address 0.0.0.0/24, Area 0 
  Process ID 20, Router ID 172.16.35.1, 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 172.16.32.2
  Suppress hello for 0 neighbor(s)

R1-7010(5)#show ip ospf interface serial 1/0
Serial1/0 is up, line protocol is up 
  Internet Address 172.16.32.2/24, Area 0 
  Process ID 20, Router ID 172.16.32.2, 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 172.16.33.1
  Suppress hello for 0 neighbor(s)

    正如前面所看到的，這兩種情況中的network-type都是點對點的。問題是一端未編號，而另一端未編號，這樣會在資料庫中產生差異，如下所示。

    R4-4K(4)#show ip ospf database router 172.16.30.1

OSPF Router with ID (172.16.35.1) (Process ID 20)
     Router Link States (Area 0)
     LS age: 202
     Options: (No TOS-capability, DC)
     LS Type: Router Links
     Link State ID: 172.16.30.1
     Advertising Router: 172.16.30.1
     LS Seq Number: 80000002
     Checksum: 0xC899
     Length: 60
     Number of Links: 3
 Link connected to: another Router (point-to-point)
     (Link ID) Neighboring Router ID: 172.16.35.1
     (Link Data) Router Interface address: 172.16.32.2
     Number of TOS metrics: 0
     TOS 0 Metrics: 64
 Link connected to: a Stub Network
     (Link ID) Network/subnet number: 172.16.32.0
     (Link Data) Network Mask: 255.255.255.0
     Number of TOS metrics: 0
     TOS 0 Metrics: 64
 Link connected to: a Stub Network
     (Link ID) Network/subnet number: 172.16.30.1
     (Link Data) Network Mask: 255.255.255.255
     Number of TOS metrics: 0
     TOS 0 Metrics: 1

R1-7010(5)#show ip ospf database router 172.16.35.1

OSPF Router with ID (172.16.30.1) (Process ID 20)
     Router Link States (Area 0)
 Adv Router is not-reachable
     LS age: 396
     Options: (No TOS-capability, DC)
     LS Type: Router Links
     Link State ID: 172.16.35.1
     Advertising Router: 172.16.35.1
     LS Seq Number: 80000003
     Checksum: 0xBEA1
     Length: 48
     Number of Links: 2
 Link connected to: another Router (point-to-point)
     (Link ID) Neighboring Router ID: 172.16.30.1
     (Link Data) Router Interface address: 0.0.0.3
          
!--- In case of an unnumbered link we use MIB-II IfIndex value which usually starts with 0.
          
     Number of TOS metrics: 0
     TOS 0 Metrics: 64
 Link connected to: a Stub Network
     (Link ID) Network/subnet number: 172.16.35.1
     (Link Data) Network Mask: 255.255.255.255
     Number of TOS metrics: 0
     TOS 0 Metrics: 1

R1-7010(5)#

    您可以看到，R1-7010使用包含其介面地址的Link Data欄位為此點對點鏈路生成LSA，而R4-4K使用包含MIB-II IfIndex值的Link Data欄位為同一鏈路生成LSA(RFC 2328)。這會導致鏈路狀態資料庫中存在不一致，這意味著路由表中未安裝任何路由。

    R1-7010(5)#show ip route
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C       172.16.32.0/24 is directly connected, Serial1/0
C       172.16.30.1/32 is directly connected, Loopback0

    解決方案

    要解決此問題，請將兩台路由器的串列介面配置為已編號或未編號。在本例中，我們對路由器R4-4K的串列2介面進行了編號。

    R4-4K(4)#configure terminal 
R4-4K(4)(config)#interface serial 2
R4-4K(4)(config-if)#no ip unnumbered loopback 0 
R4-4K(4)(config-if)#ip address 172.16.32.1 255.255.255.0

R4-4K(4))#show ip ospf interface serial 2
Serial2 is up, line protocol is up 
  Internet Address 172.16.32.1/24, Area 0 
  Process ID 20, Router ID 172.16.33.1, 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 172.16.32.2
  Suppress hello for 0 neighbor(s)

R1-7010(5)#show ip route
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C       172.16.32.0/24 is directly connected, Serial1/0
O       172.16.33.1/32 [110/65] via 172.16.32.1, 00:03:08, Serial1/0
C       172.16.30.1/32 is directly connected, Loopback0

    原因5：全網狀幀中繼環境中的PVC斷開

    請考慮以下網路圖作為範例：

    Broken PVC in Meshed Frame Relay

    R9-2500

    		 
    interface Loopback0
 ip address 10.50.50.50 255.255.255.255
 !
interface Serial0
 ip address 10.10.10.5 255.255.255.0
 encapsulation frame-relay
 ip ospf network broadcast 
 frame-relay map ip 10.10.10.6 102 broadcast
 frame-relay map ip 10.10.10.7 101 broadcast
!
router ospf 10
 network 10.10.10.0 0.0.0.255 area 0
 network 10.50.50.0 0.0.0.255 area 0

    R4-4K

    		 
    interface Loopback0
 ip address 10.70.70.70 255.255.255.255
!
interface Serial0
 ip address 10.10.10.7 255.255.255.0
 encapsulation frame-relay
 ip ospf network broadcast
 frame-relay map ip 10.10.10.5 101 broadcast
 frame-relay map ip 10.10.10.6 100 broadcast
!
router ospf 10
 network 10.10.10.0 0.0.0.255 area 0
 network 10.70.70.0 0.0.0.255 area 0

    R3-4K

    		 
    interface Loopback0
 ip address 10.60.60.60 255.255.255.255
 !
interface Serial0
 no ip address
 encapsulation frame-relay
!
interface Serial0.1 multipoint
 ip address 10.10.10.6 255.255.255.0
 ip ospf network broadcast
 frame-relay map ip 10.10.10.5 102 broadcast
 frame-relay map ip 10.10.10.7 100 broadcast
!
router ospf 10
 network 10.10.10.0 0.0.0.255 area 0
 network 10.60.60.0 0.0.0.255 area 0

    只要幀中繼網雲是全網狀的，幀中繼上的廣播模型就可以正常工作。如果任何永久虛擬電路(PVC)損壞，它可能會在OSPF資料庫中出現問題，從而產生Adv路由器無法訪問消息。

    在本示例中，R9-2500和R4-4K之間的PVC斷開，通往指定路由器(DR)的R9-2500鏈路斷開。因此，R9-2500宣告來自R3-4K（不是DR）的所有LSA不可達。您可以看到，R9-2500不會為連線到R3-4K的串列介面生成傳輸鏈路；而是生成末節鏈路，因為對於R9-2500而言，此鏈路上沒有DR。

    R9-2500(3)#show ip ospf database router

       OSPF Router with ID (10.50.50.50) (Process ID 10)
                Router Link States (Area 0)
  LS age: 148
  Options: (No TOS-capability, DC)
  LS Type: Router Links
  Link State ID: 10.50.50.50
  Advertising Router: 10.50.50.50
  LS Seq Number: 8000000B
  Checksum: 0x55A
  Length: 48
   Number of Links: 2

    Link connected to: a Stub Network
    (Link ID) Network/subnet number: 10.10.10.0
    (Link Data) Network Mask: 255.255.255.0
    Number of TOS metrics: 0
    TOS 0 Metrics: 64

    Link connected to: a Stub Network
    (Link ID) Network/subnet number: 10.50.50.50
    (Link Data) Network Mask: 255.255.255.255
    Number of TOS metrics: 0
    TOS 0 Metrics: 1

  Adv Router is not-reachable
  LS age: 1081
  Options: (No TOS-capability, DC)
  LS Type: Router Links
  Link State ID: 10.60.60.60
  Advertising Router: 10.60.60.60
  LS Seq Number: 80000006
  Checksum: 0x4F72
  Length: 48
   Number of Links: 2

    Link connected to: a Stub Network
    (Link ID) Network/subnet number: 10.60.60.60
    (Link Data) Network Mask: 255.255.255.255
    Number of TOS metrics: 0
    TOS 0 Metrics: 1

    Link connected to: a Transit Network
    (Link ID) Designated Router address: 10.10.10.7
    (Link Data) Router Interface address: 10.10.10.6
    Number of TOS metrics: 0
    TOS 0 Metrics: 64

          
  Adv Router is not-reachable
  LS age: 306
  Options: (No TOS-capability, DC)
  LS Type: Router Links
  Link State ID: 10.70.70.70
  Advertising Router: 10.70.70.70
  LS Seq Number: 80000007
  Checksum: 0xC185
  Length: 48
   Number of Links: 2

    Link connected to: a Stub Network
    (Link ID) Network/subnet number: 10.70.70.70
    (Link Data) Network Mask: 255.255.255.255
    Number of TOS metrics: 0
    TOS 0 Metrics: 1

    Link connected to: a Transit Network
    (Link ID) Designated Router address: 10.10.10.7
    (Link Data) Router Interface address: 10.10.10.7
    Number of TOS metrics: 0
    TOS 0 Metrics: 64

    有關此問題的詳細資訊，請參閱幀中繼上的NBMA和廣播模式中的OSPF問題。

    原因6：通過外部路由已知的轉發地址

    請考慮以下網路圖作為範例：

    Forwarding Address Known via an External Route

    R2507

    		 
    interface GigabitEthernet0/0
 ip address 10.1.1.1 255.255.255.0
!        
interface GigabitEthernet0/1
 ip address 10.7.7.1 255.255.255.0
!        
router ospf 1
 network 10.1.1.1 0.0.0.0 area 0
 default-information originate metric 20
!         
ip route 0.0.0.0 0.0.0.0 10.7.7.2

    R2504

    		 
    interface GigabitEthernet0/0
 ip address 10.1.1.2 255.255.255.0
!         
interface GigabitEthernet0/1
 ip address 10.3.4.2 255.255.255.0
!         
router ospf 1
 network 10.1.1.0 0.0.0.255 area 0
 network 10.0.0.0 0.255.255.255 area 1
 area 1 range 10.0.0.0 255.0.0.0

    R2515

    		 
    interface GigabitEthernet0/0
 ip address 10.3.4.3 255.255.255.0
!       
interface GigabitEthernet0/2
 ip address 10.44.66.3 255.255.255.0
!       
interface GigabitEthernet0/3
 ip address 10.22.88.3 255.255.255.0
!       
router ospf 1
 redistribute eigrp 1 metric 20 subnets
 network 0.0.0.0 255.255.255.255 area 1
!       
router eigrp 1
 network 10.3.4.0 0.0.0.255

    R2513

    		 
    interface GigabitEthernet0/0
 ip address 10.3.4.4 255.255.255.0
!       
interface GigabitEthernet0/1
 ip address 10.200.1.4 255.255.255.0
!       
router eigrp 1
 network 10.3.4.0 0.0.0.255
 network 10.200.1.0 0.0.0.255
    		 
    R2507#show ip ospf database external 10.200.1.0

            OSPF Router with ID (10.7.7.1) (Process ID 1)

                Type-5 AS External Link States

  LS age: 954
  Options: (No TOS-capability, DC, Upward)
  LS Type: AS External Link
  Link State ID: 10.200.1.0 (External Network Number )
  Advertising Router: 10.44.66.3
  LS Seq Number: 80000007
  Checksum: 0x46EF
  Length: 36
  Network Mask: /24
        Metric Type: 2 (Larger than any link state path)
        MTID: 0 
        Metric: 20 
        Forward Address: 10.3.4.4
        External Route Tag: 0

    R2507的資料庫中包含10.200.1.0/24，但它尚未將其安裝在路由表中，因為通過OSPF外部路由獲知10.3.4.4。

    R2507#show ip route 10.3.4.4
Routing entry for 10.3.4.0/24
  Known via "ospf 1", distance 110, metric 20,type extern 2, forward metric 70
  Redistributing via ospf 1
  Last update from 10.1.1.2 on GigabitEthernet0/0, 00:00:40 ago
  Routing Descriptor Blocks:
  * 10.1.1.2, from 10.44.66.3, 00:00:40 ago, via GigabitEthernet0/0
      Route metric is 20, traffic share count is 1

    注意：在此案例中，通過外部路由獲知轉發地址的原因在於下一個警告。在修復「Cisco bug ID CSCdp72526」（僅限註冊客戶）後，OSPF不會生成重疊外部網路的5類鏈路狀態通告(LSA)；因此，R2507僅顯示10.0.0.0/8的區域間總結路由。然後，R2507會安裝帶有轉發地址的10.200.1.0/24，並且可以通過區域間路由10.0.0.0/8到達，因此符合RFC 2328。

    修正提及的錯誤後，輸出如下所示：

    R2507#show ip route 10.3.4.4
Routing entry for 10.0.0.0/8
  Known via "ospf 1", distance 110, metric 2, type inter area
  Last update from 10.1.1.2 on GigabitEthernet0/0, 00:01:02 ago
  Routing Descriptor Blocks:
  * 10.1.1.2, from 10.3.4.2, 00:01:02 ago, via GigabitEthernet0/0
      Route metric is 2, traffic share count is 1  

    R2507#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is 10.7.7.2 to network 0.0.0.0

S*    0.0.0.0/0 [1/0] via 10.7.7.2
      10.0.0.0/8 is variably subnetted, 6 subnets, 3 masks
O IA     10.0.0.0/8 [110/2] via 10.1.1.2, 00:01:41, GigabitEthernet0/0
C        10.1.1.0/24 is directly connected, GigabitEthernet0/0
L        10.1.1.1/32 is directly connected, GigabitEthernet0/0
C        10.7.7.0/24 is directly connected, GigabitEthernet0/1
L        10.7.7.1/32 is directly connected, GigabitEthernet0/1
O E2 10.200.1.0/24 [110/20] via 10.1.1.2, 03:30:47, GigabitEthernet0/0

    如果轉發地址也通過外部路由得知，OSPF不會將該路由安裝到路由表中。有關此問題的更多詳細資訊，請參閱OSPF轉發地址的常見路由問題。

    原因7：路由被分發清單阻止

    下一個網路圖用作示例：

    Routes Blocked by Distribute List

    R4-4K R1-7010 
    interface Loopback0
 ip address 172.16.33.1 255.255.255.255
!
interface Serial2
 ip address 172.16.32.1 255.255.255.0
!
router ospf 20
 network 172.16.0.0 0.0.255.255 area 0
    		 
    interface Loopback0
 ip address 172.16.30.1 255.255.255.255
!
interface Serial1/0
 ip address 172.16.32.2 255.255.255.0
 clockrate 64000
!
router ospf 20
 network 172.16.0.0 0.0.255.255 area 0
 distribute-list 1 in
!
access-list 1 permit 172.16.32.0. 0.0.0.255

    如前所述，R1-7010配置了distribute-list命令，它僅允許在路由表中安裝172.16.32.0/24地址範圍。在鏈路狀態協定中，您實際上無法使用distribute-list命令篩選LSA。LSA仍存在於資料庫中；但是LSA未安裝在路由表中。

    R1-7010(5)#show ip ospf database router 172.16.33.1

  LS age: 357
  Options: (No TOS-capability, DC)
  LS Type: Router Links
  Link State ID: 172.16.33.1
  Advertising Router: 172.16.33.1
  LS Seq Number: 8000000A
  Checksum: 0xD4AA
  Length: 48
   Number of Links: 3

 Link connected to: another Router (point-to-point)
    (Link ID) Neighboring Router ID: 172.16.32.2
    (Link Data) Router Interface address: 172.16.32.1
    Number of TOS metrics: 0
    TOS 0 Metrics: 64

    R1-7010上的distribute-list配置命令過濾172.16.33.1/32網路並阻止將子網安裝到路由表中。

    R1-7010(5)#show ip route
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C       172.16.32.0/24 is directly connected, Serial1/0
C       172.16.30.1/32 is directly connected, Loopback0

    解決方案

    要解決此問題，請在訪問控制清單(ACL)中配置R1-7010並允許172.16.33.0/24，以便將此網路安裝到路由表中。

    R1-7010(5)#configure terminal 
R1-7010(5)(config)#access-list 1 permit 172.16.33.0 0.0.0.255 
R1-7010(5)(config)#end

R1-7010(5)#show ip access-list 1
Standard IP access list 1
    permit 172.16.32.0, wildcard bits 0.0.0.255
    permit 172.16.33.0, wildcard bits 0.0.0.255

R1-7010(5)#show ip route
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C       172.16.32.0/24 is directly connected, Serial1/0
O       172.16.33.1/32 [110/65] via 172.16.32.1, 00:00:08, Serial1/0
C       172.16.30.1/32 is directly connected, Loopback0

    相關資訊

    修訂記錄

    修訂 發佈日期 意見
    3.0
    28-Aug-2023
    重新認證
    2.0
    25-Jul-2022
    初始版本
    1.0
    05-Nov-2001
    初始版本
    TAC Authored

    由思科工程師貢獻

    • Julio Jimenez
      Cisco TAC Project Manager
    • Faraz Shamim
      Cisco Customer Delivery Architect

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