OSPF Router-ID

OSPF Router-IDとは

OSPFはLSAを交換することで全体のトポロジーを把握することで最短パスを計算し、ルーティングテーブルを作成しています。（参考はOSPFとは）

LSAにはそれぞれのルータを一意に識別できるIDを使ってそれぞれのルータのトポロジーを管理してている。この識別子がOSPF Route-IDになります。

OSPFのルータIDの優先順位は

ルータIDはOSPFプロセスが起動するタイミングで、下記の優先順位により決定します。

route-id コマンドで設定されたID
shutdownされていないループバックインターフェイスに設定されている最も大きいIPアドレス
shutdownされていない物理または論理インターフェイスに設定された最も大きいIPアドレス

ルータIDを変更するには、

ルータを再起動する。
ospfを無効(no router ospf )して再度ospfを有効
（※router-idコマンド時ののみ）clear ip ospf process を実行

ルータIDを変更を試してみる

R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#interface gigabitEthernet 2
R1(config-if)#ip address 192.168.0.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#end
R1#
R1#show ip int b
Interface              IP-Address      OK? Method Status                Protocol
GigabitEthernet1       10.255.0.44     YES DHCP   up                    up
GigabitEthernet2       192.168.0.1     YES manual up                    up
R1#

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#interface gigabitEthernet 2

R1(config-if)#ip address 192.168.0.1 255.255.255.0

R1(config-if)#no shutdown

R1(config-if)#end

R1#

R1#show ip int b

Interface IP-Address OK? Method Status Protocol

GigabitEthernet1 10.255.0.44 YES DHCP up up

GigabitEthernet2 192.168.0.1 YES manual up up

R1#

OSPFを起動

R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#router ospf 1
R1(config-router)#network 0.0.0.0 0.0.0.0 area 0
R1(config-router)#end
R1#
R1#show ip protocols | section ospf
Routing Protocol is "ospf 1"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Router ID 192.168.0.1
  Number of areas in this router is 1. 1 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    0.0.0.0 255.255.255.255 area 0
  Routing Information Sources:
    Gateway         Distance      Last Update
  Distance: (default is 110)
R1#

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#router ospf 1

R1(config-router)#network 0.0.0.0 0.0.0.0 area 0

R1(config-router)#end

R1#

R1#show ip protocols | section ospf

Routing Protocol is "ospf 1"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Router ID 192.168.0.1

Number of areas in this router is 1. 1 normal 0 stub 0 nssa

Maximum path: 4

Routing for Networks:

0.0.0.0 255.255.255.255 area 0

Routing Information Sources:

Gateway Distance Last Update

Distance: (default is 110)

R1#

IPで最大の192.168.0.1がroute-IDになる。

R1#
R1#conf t
R1(config)#interface loopback 0
R1(config-if)#ip address 2.2.2.2 255.255.255.255
R1(config-if)#no shutdown
R1(config-if)#end
R1#
R1#show ip int b
Interface              IP-Address      OK? Method Status                Protocol
GigabitEthernet1       10.255.0.44     YES DHCP   up                    up
GigabitEthernet2       192.168.0.1     YES manual up                    up
Loopback0              2.2.2.2         YES manual up                    up
R1#
R1#clear ip ospf process
Reset ALL OSPF processes? [no]: yes
R1#
*Dec 11 03:42:04.657: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.2 on GigabitEthernet1 from FULL to DOWN, Neighbor Down: Interface down or detached
*Dec 11 03:42:04.657: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.2 on GigabitEthernet2 from FULL to DOWN, Neighbor Down: Interface down or detached
*Dec 11 03:42:04.662: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.2 on GigabitEthernet1 from LOADING to FULL, Loading Done
*Dec 11 03:42:04.663: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.2 on GigabitEthernet2 from LOAD
R1#ING to FULL, Loading Done
R1#
R1#show ip protocols | s ospf
Routing Protocol is "ospf 1"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Router ID 192.168.0.1
  Number of areas in this router is 1. 1 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    0.0.0.0 255.255.255.255 area 0
  Routing Information Sources:
    Gateway         Distance      Last Update
     192.168.0.2          110      00:01:37
    192.168.0.2          110      00:01:37
  Distance: (default is 110)
R1#

R1#

R1#conf t

R1(config)#interface loopback 0

R1(config-if)#ip address 2.2.2.2 255.255.255.255

R1(config-if)#no shutdown

R1(config-if)#end

R1#

R1#show ip int b

Interface IP-Address OK? Method Status Protocol

GigabitEthernet1 10.255.0.44 YES DHCP up up

GigabitEthernet2 192.168.0.1 YES manual up up

Loopback0 2.2.2.2 YES manual up up

R1#

R1#clear ip ospf process

Reset ALL OSPF processes? [no]: yes

R1#

*Dec 11 03:42:04.657: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.2 on GigabitEthernet1 from FULL to DOWN, Neighbor Down: Interface down or detached

*Dec 11 03:42:04.657: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.2 on GigabitEthernet2 from FULL to DOWN, Neighbor Down: Interface down or detached

*Dec 11 03:42:04.662: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.2 on GigabitEthernet1 from LOADING to FULL, Loading Done

*Dec 11 03:42:04.663: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.2 on GigabitEthernet2 from LOAD

R1#ING to FULL, Loading Done

R1#

R1#show ip protocols | s ospf

Routing Protocol is "ospf 1"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Router ID 192.168.0.1

Number of areas in this router is 1. 1 normal 0 stub 0 nssa

Maximum path: 4

Routing for Networks:

0.0.0.0 255.255.255.255 area 0

Routing Information Sources:

Gateway Distance Last Update

192.168.0.2 110 00:01:37

Distance: (default is 110)

R1#

Loopbackを追加してclear ip ospf processを実行しても反映されない。

R1#copy running-config startup-config
Destination filename [startup-config]?
Building configuration...
[OK]
R1#reload
Proceed with reload? [confirm]

/snip/

R1#show ip protocols | s ospf
Routing Protocol is "ospf 1"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Router ID 2.2.2.2
  Number of areas in this router is 1. 1 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    0.0.0.0 255.255.255.255 area 0
  Routing Information Sources:
    Gateway         Distance      Last Update
  Distance: (default is 110)
R1#

R1#copy running-config startup-config

Destination filename [startup-config]?

Building configuration...

[OK]

R1#reload

Proceed with reload? [confirm]

/snip/

R1#show ip protocols | s ospf

Routing Protocol is "ospf 1"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Router ID 2.2.2.2

Number of areas in this router is 1. 1 normal 0 stub 0 nssa

Maximum path: 4

Routing for Networks:

0.0.0.0 255.255.255.255 area 0

Routing Information Sources:

Gateway Distance Last Update

Distance: (default is 110)

R1#

再起動することでroute-idが変更された。

R1#conf t
R1(config)#router ospf 1
R1(config-router)#router-id 1.1.1.1
% OSPF: Reload or use "clear ip ospf process" command, for this to take effect
R1(config-router)#end
R1#sho ip protocols | section ospf
Routing Protocol is "ospf 1"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Router ID 2.2.2.2
  Number of areas in this router is 1. 1 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    0.0.0.0 255.255.255.255 area 0
  Routing Information Sources:
    Gateway         Distance      Last Update
     192.168.0.2          110      00:01:17
    192.168.0.2          110      00:01:17
  Distance: (default is 110)
R1#
R1#clear ip ospf process
Reset ALL OSPF processes? [no]: yes
R1#
*Dec 11 03:47:35.108: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.2 on GigabitEthernet1 from FULL to DOWN, Neighbor Down: Interface down or detached
*Dec 11 03:47:35.108: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.2 on GigabitEthernet2 from FULL to DOWN, Neighbor Down: Interface down or detached
R1#
R1#sho ip protocols | section ospf
Routing Protocol is "ospf 1"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Router ID 1.1.1.1
  Number of areas in this router is 1. 1 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    0.0.0.0 255.255.255.255 area 0
  Routing Information Sources:
    Gateway         Distance      Last Update
     192.168.0.2          110      00:02:17
    192.168.0.2          110      00:02:17
  Distance: (default is 110)
R1#

R1#conf t

R1(config)#router ospf 1

R1(config-router)#router-id 1.1.1.1

% OSPF: Reload or use "clear ip ospf process" command, for this to take effect

R1(config-router)#end

R1#sho ip protocols | section ospf

Routing Protocol is "ospf 1"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Router ID 2.2.2.2

Number of areas in this router is 1. 1 normal 0 stub 0 nssa

Maximum path: 4

Routing for Networks:

0.0.0.0 255.255.255.255 area 0

Routing Information Sources:

Gateway Distance Last Update

192.168.0.2 110 00:01:17

Distance: (default is 110)

R1#

R1#clear ip ospf process

Reset ALL OSPF processes? [no]: yes

R1#

*Dec 11 03:47:35.108: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.2 on GigabitEthernet1 from FULL to DOWN, Neighbor Down: Interface down or detached

*Dec 11 03:47:35.108: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.2 on GigabitEthernet2 from FULL to DOWN, Neighbor Down: Interface down or detached

R1#

R1#sho ip protocols | section ospf

Routing Protocol is "ospf 1"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Router ID 1.1.1.1

Number of areas in this router is 1. 1 normal 0 stub 0 nssa

Maximum path: 4

Routing for Networks:

0.0.0.0 255.255.255.255 area 0

Routing Information Sources:

Gateway Distance Last Update

192.168.0.2 110 00:02:17

Distance: (default is 110)

R1#

router-idを設定すると再起動もしくはclear ip ospf processを実行後に反映されるとのメッセージが表示されるので、clear ip ospf processで反映される。

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