ネットワーク構成
下記のネットワーク構成でOSPFの設定を行っています。シングルエリア構成で、エリアは0です。
図 OSPFのトラブルネットワーク構成
トラブルの状況
ネットワークの一部で通信ができない状況が発生しています。ルーティングのトラブルが発生しているようです。ルーティングが正常に行われているかを確認するために、各ルータでshow ip ospf neighborをみたところ、すべてFULL状態になっているのでネイバーは問題なく確立されているようです。
R1 show ip ospf neighbor ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 192.168.3.3 0 FULL/ - 00:00:38 192.168.123.3 FastEthernet0/0 192.168.2.2 0 FULL/ - 00:00:33 192.168.123.2 FastEthernet0/0 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ R2 show ip ospf neighbor ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ R2#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 192.168.1.1 1 FULL/DROTHER 00:00:34 192.168.123.1 FastEthernet0/0 192.168.3.3 1 FULL/BDR 00:00:32 192.168.123.3 FastEthernet0/0 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ R3 show ip ospf neighbor ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ R3#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 192.168.1.1 1 FULL/DROTHER 00:00:37 192.168.123.1 FastEthernet0/0 192.168.2.2 1 FULL/DR 00:00:30 192.168.123.2 FastEthernet0/0 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
ところが、ルーティングテーブルには必要なルート情報が登録されていません。
R1 show ip route
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R1#show ip route
～省略～
Gateway of last resort is not set
C 192.168.123.0/24 is directly connected, FastEthernet0/0
192.168.1.0/32 is subnetted, 1 subnets
C 192.168.1.1 is directly connected, Loopback0
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R2 show ip route
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R2#show ip route
～省略～
Gateway of last resort is not set
C 192.168.123.0/24 is directly connected, FastEthernet0/0
192.168.2.0/32 is subnetted, 1 subnets
C 192.168.2.2 is directly connected, Loopback0
192.168.3.0/32 is subnetted, 1 subnets
O 192.168.3.3 [110/2] via 192.168.123.3, 00:18:37, FastEthernet0/0
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
R3 show ip route
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R3#show ip route
～省略～
Gateway of last resort is not set
C 192.168.123.0/24 is directly connected, FastEthernet0/0
192.168.2.0/32 is subnetted, 1 subnets
O 192.168.2.2 [110/2] via 192.168.123.2, 00:19:33, FastEthernet0/0
192.168.3.0/32 is subnetted, 1 subnets
C 192.168.3.3 is directly connected, Loopback0
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
もう少し詳しい状況を確認するために、show ip ospf interfaceコマンドの出力を見ると、次のようになりました。
R1 show ip ospf interface
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R1#show ip ospf interface
Loopback0 is up, line protocol is up
Internet Address 192.168.1.1/32, Area 0
Process ID 1, Router ID 192.168.1.1, Network Type LOOPBACK, Cost: 1
Loopback interface is treated as a stub Host
FastEthernet0/0 is up, line protocol is up
Internet Address 192.168.123.1/24, Area 0
Process ID 1, Router ID 192.168.1.1, Network Type POINT_TO_MULTIPOINT, Cost: 1
Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:07
Supports Link-local Signaling (LLS)
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 2, Adjacent neighbor count is 2
Adjacent with neighbor 192.168.3.3
Adjacent with neighbor 192.168.2.2
Suppress hello for 0 neighbor(s)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
R2 show ip ospf interface
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R2#show ip ospf interface
Loopback0 is up, line protocol is up
Internet Address 192.168.2.2/32, Area 0
Process ID 1, Router ID 192.168.2.2, Network Type LOOPBACK, Cost: 1
Loopback interface is treated as a stub Host
FastEthernet0/0 is up, line protocol is up
Internet Address 192.168.123.2/24, Area 0
Process ID 1, Router ID 192.168.2.2, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 192.168.2.2, Interface address 192.168.123.2
Backup Designated router (ID) 192.168.3.3, Interface address 192.168.123.3
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:07
Supports Link-local Signaling (LLS)
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 4 msec
Neighbor Count is 2, Adjacent neighbor count is 2
Adjacent with neighbor 192.168.1.1
Adjacent with neighbor 192.168.3.3 (Backup Designated Router)
Suppress hello for 0 neighbor(s)
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R3 show ip ospf interface
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R3#show ip ospf interface
Loopback0 is up, line protocol is up
Internet Address 192.168.3.3/32, Area 0
Process ID 1, Router ID 192.168.3.3, Network Type LOOPBACK, Cost: 1
Loopback interface is treated as a stub Host
FastEthernet0/0 is up, line protocol is up
Internet Address 192.168.123.3/24, Area 0
Process ID 1, Router ID 192.168.3.3, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State BDR, Priority 1
Designated Router (ID) 192.168.2.2, Interface address 192.168.123.2
Backup Designated router (ID) 192.168.3.3, Interface address 192.168.123.3
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:08
Supports Link-local Signaling (LLS)
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 0, maximum is 1
Last flood scan time is 0 msec, maximum is 4 msec
Neighbor Count is 2, Adjacent neighbor count is 2
Adjacent with neighbor 192.168.1.1
Adjacent with neighbor 192.168.2.2 (Designated Router)
Suppress hello for 0 neighbor(s)
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～トラブルの解決
show ip ospf interfaceの出力を見ることで、あるルータでの設定ミスが判明しました。その設定ミスを修正すると、正常にルーティングが行えるようになりました。
[問題]- どのルータでどのような設定ミスのため、このトラブルが起こっているでしょうか？
- その設定ミスに関わらずなぜネイバーはすべてFULL状態になるのでしょうか？
