Implementing Single-Area OSPFv2
Using OSPFv2 Interface Subcommands
- OSPF Interface Configuration Example
  - Verifying OSPF Interface Configuration
Additional OSPFv2 Features

Implementing Single-Area OSPFv2

OSPF Single-Area Configuration

f:id:wand_ta:20200510002631p:plain

R2の設定

R2#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#router ospf 1
R2(config-router)#network 10.0.0.0 0.255.255.255 area 0

router ospf 1
- process id
- 1-65535のなんでもいい
0.255.255.255: wildcard mask

Wikdcard Matching with the network Command

0.255.255.255
- 下位3オクテットは問わない、の意
R3も設定

R3#config terminal
Enter configuration commands, one per line.  End with CNTL/Z.
R3(config)#router ospf 1
R3(config-router)#network 10.1.13.0 0.0.0.255 area 0
R3(config-router)#network 10.1.23.0 0.0.0.255 area 0

R2とR3がfull stateになる

%SYS-5-CONFIG_I: Configured from console by console

00:17:11: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.23.2 on GigabitEthernet0/0/1 from LOADING to FULL, Loading Done

R4も設定

R4(config)#router ospf 1
R4(config-router)#network 10.1.14.4 0.0.0.0 area 0
R4(config-router)#network 10.1.4.4 0.0.0.0 area 0

R1も設定、全router設定完了

R1(config)#router ospf 1
R1(config-router)#network 10.0.0.0 0.255.255.255 area 0
R1(config-router)#

Verifying OSPF Operation

R1#show ip ospf neighbor


Neighbor ID     Pri   State           Dead Time   Address         Interface
10.1.23.2         1   FULL/DR         00:00:33    10.1.12.2       GigabitEthernet4/0
10.1.23.3         1   FULL/DR         00:00:32    10.1.13.3       GigabitEthernet5/0
10.1.14.4         1   FULL/DR         00:00:38    10.1.14.4       GigabitEthernet6/0
R1#

R2#show ip ospf neighbor 


Neighbor ID     Pri   State           Dead Time   Address         Interface
10.1.14.1         1   FULL/BDR        00:00:35    10.1.12.1       GigabitEthernet0/0/0
10.1.23.3         1   FULL/BDR        00:00:31    10.1.23.3       GigabitEthernet0/0/1
R2#

R3>show ip ospf neighbor 


Neighbor ID     Pri   State           Dead Time   Address         Interface
10.1.14.1         1   FULL/BDR        00:00:33    10.1.13.1       GigabitEthernet0/0/0
10.1.23.2         1   FULL/DR         00:00:38    10.1.23.2       GigabitEthernet0/0/1
R3>

Neighbor ID     Pri   State           Dead Time   Address         Interface
10.1.14.1         1   FULL/BDR        00:00:33    10.1.14.1       GigabitEthernet0/0/0
R4>

FULL/DR: full stateで、相手がDRの意
FULL/BDR: full stateで、相手がBDRの意

R1#show ip route
Codes: C - connected, S - static, I - IGRP, 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, E - EGP
       i - IS-IS, 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

Gateway of last resort is not set

     10.0.0.0/24 is subnetted, 7 subnets
C       10.1.1.0 is directly connected, GigabitEthernet2/0.10
C       10.1.2.0 is directly connected, GigabitEthernet2/0.20
O       10.1.4.0 [110/2] via 10.1.14.4, 00:06:15, GigabitEthernet6/0
C       10.1.12.0 is directly connected, GigabitEthernet4/0
C       10.1.13.0 is directly connected, GigabitEthernet5/0
C       10.1.14.0 is directly connected, GigabitEthernet6/0
O       10.1.23.0 [110/2] via 10.1.12.2, 00:06:15, GigabitEthernet4/0
                  [110/2] via 10.1.13.3, 00:06:15, GigabitEthernet5/0

R1#

PC0(10.1.1.11)からPC3(10.1.4.11)にpingしてみる

C:\>ping 10.1.4.11

Pinging 10.1.4.11 with 32 bytes of data:

Reply from 10.1.4.11: bytes=32 time<1ms TTL=126
Reply from 10.1.4.11: bytes=32 time<1ms TTL=126
Reply from 10.1.4.11: bytes=32 time<1ms TTL=126
Reply from 10.1.4.11: bytes=32 time<1ms TTL=126

Ping statistics for 10.1.4.11:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 0ms, Maximum = 0ms, Average = 0ms

Verifying OSPF Configuration

show running-commandが一番
show ip protocolsも使える
- enable不要

R3>show ip protocols 

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 10.1.23.3
  Number of areas in this router is 1. 1 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    10.1.13.0 0.0.0.255 area 0
    10.1.23.0 0.0.0.255 area 0
  Routing Information Sources:  
    Gateway         Distance      Last Update 
    10.1.14.1            110      00:11:39
    10.1.14.4            110      00:11:40
    10.1.23.2            110      00:11:44
    10.1.23.3            110      00:11:39
  Distance: (default is 110)

R3>

R3>show ip ospf interface g0/0/0

GigabitEthernet0/0/0 is up, line protocol is up
  Internet address is 10.1.13.3/24, Area 0
  Process ID 1, Router ID 10.1.23.3, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router (ID) 10.1.23.3, Interface address 10.1.13.3
  Backup Designated Router (ID) 10.1.14.1, Interface address 10.1.13.1
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:01
  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 1, Adjacent neighbor count is 1
    Adjacent with neighbor 10.1.14.1  (Backup Designated Router)
  Suppress hello for 0 neighbor(s)
R3>

show ip ospf interface briefでinterfaceをリストできるはずだがPacket Tracerでは動作せず
- networkコンフィグで意図せぬinterfaceが設定されていないことの確認
  - ワイルドカードマスク設定間違いなど

Configurating the OSPF Router ID

R1#show ip ospf neighbor 


Neighbor ID     Pri   State           Dead Time   Address         Interface
10.1.23.2         1   FULL/DR         00:00:33    10.1.12.2       GigabitEthernet4/0
10.1.23.3         1   FULL/DR         00:00:33    10.1.13.3       GigabitEthernet5/0
10.1.14.4         1   FULL/DR         00:00:39    10.1.14.4       GigabitEthernet6/0
R1#

↑のNeighbor IDを設定できる

R1(config)#router ospf 1
R1(config-router)#router-id 1.1.1.1
R1(config-router)#Reload or use "clear ip ospf process" command, for this to take effect


R1(config-router)#end
R1#
%SYS-5-CONFIG_I: Configured from console by console

設定を反映するためにリロード

R1#clear ip ospf process
Reset ALL OSPF processes? [no]: yes

R1#
00:54:02: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.23.2 on GigabitEthernet4/0 from FULL to DOWN, Neighbor Down: Adjacency forced to reset

00:54:02: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.23.2 on GigabitEthernet4/0 from FULL to DOWN, Neighbor Down: Interface down or detached

00:54:02: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.23.3 on GigabitEthernet5/0 from FULL to DOWN, Neighbor Down: Adjacency forced to reset

00:54:02: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.23.3 on GigabitEthernet5/0 from FULL to DOWN, Neighbor Down: Interface down or detached

00:54:02: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.14.4 on GigabitEthernet6/0 from FULL to DOWN, Neighbor Down: Adjacency forced to reset

00:54:02: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.14.4 on GigabitEthernet6/0 from FULL to DOWN, Neighbor Down: Interface down or detached

R1#
R1#
R1#
00:54:07: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.14.4 on GigabitEthernet6/0 from LOADING to FULL, Loading Done

00:54:12: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.23.3 on GigabitEthernet5/0 from LOADING to FULL, Loading Done

00:54:13: %OSPF-5-ADJCHG: Process 1, Nbr 10.1.23.2 on GigabitEthernet4/0 from LOADING to FULL, Loading Done

他のルータから見たR1のRIDが変わる

00:54:13: %OSPF-5-ADJCHG: Process 1, Nbr 1.1.1.1 on GigabitEthernet0/0/0 from LOADING to FULL, Loading Done


R2#show ip ospf neighbor


Neighbor ID     Pri   State           Dead Time   Address         Interface
1.1.1.1           1   FULL/BDR        00:00:30    10.1.12.1       GigabitEthernet0/0/0
10.1.23.3         1   FULL/BDR        00:00:37    10.1.23.3       GigabitEthernet0/0/1
R2#

loopback interfaceにRIDとして使いたいIPアドレスを振っておくという方法もある

R2#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#interface loopback2
R2(config-if)#ip address 2.2.2.2 255.255.255.255
R2(config-if)#

所定のRIDになっていることの確認

R1#show ip ospf
 Routing Process "ospf 1" with ID 1.1.1.1
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
 Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
 Number of external LSA 0. Checksum Sum 0x000000
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 0
 Number of areas in this router is 1. 1 normal 0 stub 0 nssa
 External flood list length 0
    Area BACKBONE(0)
        Number of interfaces in this area is 5
        Area has no authentication
        SPF algorithm executed 9 times
        Area ranges are
        Number of LSA 9. Checksum Sum 0x049cdd
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0

R1#

Implementing Multiarea OSPF

f:id:wand_ta:20200510002752p:plain

R1(config)#no router ospf 1
R1(config)#router ospf 1
R1(config-router)#network 10.1.1.1 0.0.0.0 area 0
R1(config-router)#network 10.1.2.1 0.0.0.0 area 0
R1(config-router)#network 10.1.12.1 0.0.0.0 area 23
R1(config-router)#network 10.1.13.1 0.0.0.0 area 23
R1(config-router)#network 10.1.14.1 0.0.0.0 area 4

R2(config)#no router ospf 1
R2(config)#router ospf 1
R2(config-router)#network 10.0.0.0 0.255.255.255 area 23

R3(config)#no router ospf 1
R3(config)#router ospf 1
R3(config-router)#network 10.0.0.0 0.255.255.255 area 23

R4(config)#no router ospf 1
R4(config)#router ospf 1
R4(config-router)#network 10.0.0.0 0.255.255.255 area 4

確認

R1>show ip protocols

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 3. 3 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    10.1.1.1 0.0.0.0 area 0
    10.1.2.1 0.0.0.0 area 0
    10.1.12.1 0.0.0.0 area 23
    10.1.13.1 0.0.0.0 area 23
    10.1.14.1 0.0.0.0 area 4
  Routing Information Sources:  
    Gateway         Distance      Last Update 
    1.1.1.1              110      00:00:31
    2.2.2.2              110      00:00:21
    3.3.3.3              110      00:00:26
    4.4.4.4              110      00:00:31
  Distance: (default is 110)

R1>enable
R1#show ip ospf neighbor


Neighbor ID     Pri   State           Dead Time   Address         Interface
3.3.3.3           1   FULL/DR         00:00:34    10.1.13.3       GigabitEthernet5/0
2.2.2.2           1   FULL/DR         00:00:34    10.1.12.2       GigabitEthernet4/0
4.4.4.4           1   FULL/DR         00:00:34    10.1.14.4       GigabitEthernet6/0
R1#

Using OSPFv2 Interface Subcommands

router ospf 1とかnetworkとか使うのは古いですよという話

OSPF Interface Configuration Example

まずまっさらに

R1(config)#no router ospf 1

各interfaceでip ospf <process_id> area <area_id>

R1(config)#interface g2/0.10
R1(config-subif)#ip ospf 1 area 0
R1(config-subif)#interface g2/0.20
R1(config-subif)#ip ospf 1 area 0
R1(config-subif)#interface g4/0
R1(config-if)#ip ospf 1 area 23
R1(config-if)#interface g5/0
R1(config-if)#ip ospf 1 area 23
R1(config-if)#interface g6/0
R1(config-if)#ip ospf 1 area 4

他のルータも

R4(config-if)#ip address 4.4.4.4 255.255.255.0
R4(config-if)#
R4(config-if)#no router ospf 1
R4(config)#interface range g0/0/0-1
R4(config-if-range)#ip ospf 1 area 4

Verifying OSPF Interface Configuration

設定確認

R1>show ip protocols

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 3. 3 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
  Routing Information Sources:  
    Gateway         Distance      Last Update 
    1.1.1.1              110      00:01:12
    2.2.2.2              110      00:01:07
    3.3.3.3              110      00:01:07
    4.4.4.4              110      00:01:12
  Distance: (default is 110)

Routing for Networks:の後にRouting on Interfaces Configures Explicitly (Area 0)とか出るはずなのだがPacket Tracerだからか出てこず
設定確認2

R1#show ip ospf interface g4/0

GigabitEthernet4/0 is up, line protocol is up
  Internet address is 10.1.12.1/24, Area 23
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State BDR, Priority 1
  Designated Router (ID) 2.2.2.2, Interface address 10.1.12.2
  Backup Designated Router (ID) 1.1.1.1, Interface address 10.1.12.1
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:07
  Index 3/3, 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 1, Adjacent neighbor count is 1
    Adjacent with neighbor 2.2.2.2  (Designated Router)
  Suppress hello for 0 neighbor(s)
R1#

Internet address is 10.1.12.1/24, Area 23の後にAttached via Interface Enableとか出るはずなのだがやはり出てこず
- router ospf,networkで指定した場合はAttached via Network Statement

Additional OSPFv2 Features

OSPF Passive Interfaces

OSPFがenabledになったinterfaceは、Hello送出・リッスンするようになる
Hello送出・リッスンをやめたいケースがある
- 例:R1のg2/0 (左), R4のg0/0/1 (右)
  - subnetの情報は必要なので、networkやip ospf <process_id> area <area_id>などの設定自体は必要
  - が、その先にrouterがいないので、Helloを送るだけ無駄

f:id:wand_ta:20200510002920p:plain

Passive Interfacesの設定

R1(config)#router ospf 1
R1(config-router)#passive-interface g2/0.10
R1(config-router)#passive-interface g2/0.20

R4(config)#router ospf 1
R4(config-router)#passive-interface g0/0/1

無駄なHelloが飛ばなくなる

f:id:wand_ta:20200510002956p:plain

設定確認

R1#show ip ospf interface g2/0
%OSPF: OSPF not enabled on GigabitEthernet2/0
R1#show ip ospf interface g2/0.10

GigabitEthernet2/0.10 is up, line protocol is up
  Internet address is 10.1.1.1/24, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State WAITING, Priority 1
  No designated router on this network
  No backup designated router on this network
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    No Hellos (Passive interface)
  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 0, Adjacent neighbor count is 0
  Suppress hello for 0 neighbor(s)
R1#

    No Hellos (Passive interface)

OSPF Default Routes

インターネットに面しているrouterを新たに設置したとする

f:id:wand_ta:20200510003207p:plain

ISP1(config-if)#interface g0/0/0
ISP1(config-if)#no shutdown
ISP1(config-if)#ip address 192.168.11.1 255.255.255.0
ISP1(config-if)#ip route 10.0.0.0 255.0.0.0 192.168.11.2

ISP1#show ip route
...
S    10.0.0.0/8 [1/0] via 192.168.11.2
     192.168.11.0/24 is variably subnetted, 2 subnets, 2 masks
...

新たなISP1をR1のg9/0に繋いだ

R1(config-router)#interface g9/0
R1(config-if)#ip address 192.168.11.2 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#ip route 0.0.0.0 0.0.0.0 192.168.11.1

R1#show ip route
...
S*   0.0.0.0/0 [1/0] via 192.168.11.1

インターネット上のIPアドレスにアクセスするときは、ISP1ルータにルーティングするようにR1に設定した (last resort gateway)
last resort gatewayを他のrouterにも教えてあげたいとき:

R1(config-router)#default-information originate

R2のrouting tableの確認

R2>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, E - EGP
       i - IS-IS, 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

Gateway of last resort is 10.1.12.1 to network 0.0.0.0

     2.0.0.0/32 is subnetted, 1 subnets
C       2.2.2.2/32 is directly connected, Loopback2
     10.0.0.0/8 is variably subnetted, 9 subnets, 2 masks
O IA    10.1.1.0/24 [110/2] via 10.1.12.1, 00:22:08, GigabitEthernet0/0/0
O IA    10.1.2.0/24 [110/2] via 10.1.12.1, 00:22:08, GigabitEthernet0/0/0
O IA    10.1.4.0/24 [110/3] via 10.1.12.1, 00:22:08, GigabitEthernet0/0/0
C       10.1.12.0/24 is directly connected, GigabitEthernet0/0/0
L       10.1.12.2/32 is directly connected, GigabitEthernet0/0/0
O       10.1.13.0/24 [110/2] via 10.1.12.1, 00:19:30, GigabitEthernet0/0/0
                     [110/2] via 10.1.23.3, 00:19:30, GigabitEthernet0/0/1
O IA    10.1.14.0/24 [110/2] via 10.1.12.1, 00:22:08, GigabitEthernet0/0/0
C       10.1.23.0/24 is directly connected, GigabitEthernet0/0/1
L       10.1.23.2/32 is directly connected, GigabitEthernet0/0/1
O*E2 0.0.0.0/0 [110/1] via 10.1.12.1, 00:05:11, GigabitEthernet0/0/0

R2にもlast resort gatewayが追加されている！

O*E2 0.0.0.0/0 [110/1] via 10.1.12.1, 00:05:11, GigabitEthernet0/0/0

PCでping 8.8.8.8とかやると、ちゃんとISP1までパケットが届く

f:id:wand_ta:20200510003542p:plain

OSPF Metrics (Cost)

R1#show ip ospf interface g2/0.10

GigabitEthernet2/0.10 is up, line protocol is up
  Internet address is 10.1.1.1/24, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
...

これ: Cost: 1
算出の公式

ospf_cost = ceil(reference_bandwidth / interface_bandwidth)

コストの設定方法
- interfaceごとに直接costを設定する
- interface bandwidthを設定し、cost算出は公式に委ねる
- reference bandwidthを設定し、cost算出は公式に委ねる
  - デフォルト100,000 kbps
直接設定

R1(config)#interface g2/0.10
R1(config-subif)#ip ospf cost 10

R1#show ip ospf interface g2/0.10

GigabitEthernet2/0.10 is up, line protocol is up
  Internet address is 10.1.1.1/24, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 10

interfaceのbandwidth設定
- kbps単位

R1(config)#interface g2/0.10
R1(config-subif)#bandwidth 1000
R1(config-subif)#interface g2/0.20
R1(config-subif)#bandwidth 1000
R1(config-subif)#end

100000/1000で100になるはず

R1#show ip ospf interface g2/0.10

GigabitEthernet2/0.10 is up, line protocol is up
  Internet address is 10.1.1.1/24, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 10
  ...

R1はcost直接指定(10)のほうが強い

R1#show ip ospf interface g2/0.20

GigabitEthernet2/0.20 is up, line protocol is up
  Internet address is 10.1.2.1/24, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 100
  ...

R2は計算通り
続いて、reference bandwidthの設定
- こちらはMbps単位

R1(config)#router ospf 1
R1(config-router)#auto-cost reference-bandwidth 50
% OSPF: Reference bandwidth is changed.
        Please ensure reference bandwidth is consistent across all routers.

全routerで揃えてね、と言われる

R1#show ip ospf interface g2/0.20

GigabitEthernet2/0.20 is up, line protocol is up
  Internet address is 10.1.2.1/24, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 50

50Mbps / 1000kbps = 50になった

OSPF Load Balancing

メトリクスの等しいrouteが複数ある場合、負荷分散される
「メトリクスの等しいroute」はデフォルトで4本までだったりする
これを増やすにはrouter ospfの下でmaximum-paths <number>を設定する
負荷分散方式はデフォルトでper-destination IP

勉強日記

チラ裏

CCNA試験対策 ch20 Implementing OSPF