Configurar as Configurações Iniciais do OSPF em Links Não-Broadcast

Introduction

Este documento descreve as configurações iniciais para Open Shortest Path First (OSPF) em links sem broadcast.

Informações de Apoio

Em mídias non-broadcast como Frame Relay, X.25, ATM e Switched Multimegabit Data Service (SMDS), o OSPF pode executar em dois modos:

• Nonbroadcast Multiaccess (NBMA): simula um modelo de broadcast pela eleição de um roteador designado (DR) e um roteador designado de backup (BDR). Há duas maneiras de simular um modelo de broadcast em uma rede NBMA: defina o tipo de rede como broadcast com o subcomando da interface ip ospf network broadcast ou configure as instruções vizinhas que usam o comando router ospf.

• Ponto a multiponto: trata a rede sem broadcast como uma coleção de links ponto a ponto pela configuração do comando ip ospf network point-to-multipoint.

Você deve definir o tipo de rede em redes sem broadcast para evitar a configuração de instruções de vizinhos. Este documento fornece configurações de exemplo para OSPF em links sem broadcast. Use o comando show ip ospf interface para verificar o tipo de rede de uma interface que executa o OSPF e o comando show ip ospf neighbor é usado para saber o status do roteador vizinho.

Prerequisites

Requirements

A Cisco recomenda que você compreenda a configuração básica do protocolo de roteamento OSPF .

Componentes Utilizados

As informações neste documento são baseadas nestas versões de software e hardware:

• Roteadores Cisco 2500

• Software Cisco IOS^® versão 12.2(24a) executado em roteadores

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. Se a rede estiver ativa, certifique-se de que você entenda o impacto potencial de qualquer comando.

Diagrama de Rede

Este é o diagrama de rede usado nos exemplos de configuração neste documento.

Configurações para NBMA (Usar Broadcast de Tipo de Rede)

interface Loopback0
      ip address 192.0.2.3 255.255.255.255
     !
     !
     interface Serial2
      ip address 192.0.2.1 255.255.255.0
      encapsulation frame-relay
      ip ospf network broadcast
      no keepalive
      frame-relay map ip 192.0.2.1 16 broadcast
     !
     !
     router ospf 1
      network 192.0.2.0 0.0.0.255 area 0

interface Loopback0
      ip address 192.0.2.2 255.255.255.255
     !
     interface Serial1/0
      ip address 192.0.2.1 255.255.255.0
      encapsulation frame-relay
      ip ospf network broadcast
      no keepalive
      clockrate 2000000
      frame-relay map ip 192.0.2.1 16 broadcast
     !
     router ospf 1
      network 192.0.2.0 0.0.0.255 area 0
     !

Dicas de verificação

Esta é a saída do comando show para o Roteador 1.

Router1# show ip ospf neighbor
      
     Neighbor ID     Pri   State           Dead Time   Address         Interface
     192.0.2.2           1   FULL/BDR        00:00:37    192.0.2.1         Serial2
     
Router1# show ip ospf interface s2
     Serial2 is up, line protocol is up 
       Internet Address 192.0.2.1/24, Area 0 
       Process ID 1, Router ID 192.0.2.3, Network Type BROADCAST, Cost: 64
       Transmit Delay is 1 sec, State DR, Priority 1 
       Designated Router (ID) 192.0.2.3, Interface address 192.0.2.1
       Backup Designated router (ID) 192.0.2.2, Interface address 192.0.2.1
       Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
         Hello due in 00:00:00
       Index 1/1, flood queue length 0
       Next 0x0(0)/0x0(0)
       Last flood scan length is 1, maximum is 2
       Last flood scan time is 0 msec, maximum is 4 msec
       Neighbor Count is 1, Adjacent neighbor count is 1 
         Adjacent with neighbor 192.0.2.2  (Backup Designated Router)
       Suppress hello for 0 neighbor(s)

E a saída para o Roteador 2 é a seguinte:

Router2# show ip ospf neighbor
      
     Neighbor ID     Pri   State           Dead Time   Address         Interface
     192.0.2.3           1   FULL/DR         00:00:38     192.0.2.1         Serial1/0
     
Router2# show ip ospf interface s1/0
     Serial1/0 is up, line protocol is up 
       Internet Address 192.0.2.1/24, Area 0 
       Process ID 1, Router ID 192.0.2.2, Network Type BROADCAST, Cost: 64
       Transmit Delay is 1 sec, State BDR, Priority 1 
       Designated Router (ID) 192.0.2.3, Interface address 192.0.2.1
       Backup Designated router (ID) 192.0.2.2, Interface address 192.0.2.1
       Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
         Hello due in 00:00:03
       Index 1/1, flood queue length 0
       Next 0x0(0)/0x0(0)
       Last flood scan length is 1, maximum is 2
       Last flood scan time is 0 msec, maximum is 4 msec
       Neighbor Count is 1, Adjacent neighbor count is 1 
         Adjacent with neighbor 192.0.2.3  (Designated Router)
       Suppress hello for 0 neighbor(s)

Configurações para NBMA (usar instruções de vizinhos)

interface Loopback0
      ip address 192.0.2.3 255.255.255.255
     !
     interface Serial2
      ip address 192.0.2.1 255.255.255.0
      encapsulation frame-relay
      ip ospf priority 2
      no keepalive
      frame-relay map ip 192.0.2.1 16
     !
     router ospf 1
      network 192.0.2.0 0.0.0.255 area 0
      neighbor 192.0.2.1
     !

interface Loopback0
      ip address 192.0.2.2 255.255.255.255
     !
     interface Serial1/0
      ip address 192.0.2.1 255.255.255.0
      encapsulation frame-relay
      no keepalive
      clockrate 2000000
      frame-relay map ip 192.0.2.1 16
     !
     router ospf 1
      network 192.0.2.0 0.0.0.255 area 0
      neighbor 192.0.2.1
     !

Observação: nas configurações mostradas, o comando ip ospf priority 2 no Router1 define uma prioridade de interface mais alta do que o valor de prioridade padrão 1, o que o torna um DR e o Router2 o BDR para a rede NBMA. Se necessário, você pode definir o valor de prioridade como 0 para configurar um roteador para nunca se tornar um DR/BDR. Isso é necessário em redes de hub e spoke onde o hub deve ser configurado para se tornar o DR, enquanto os spokes não devem ser DR nem BDR. Embora a configuração da instrução neighbor em uma extremidade seja suficiente para formar adjacência, é uma boa prática tê-la configurada em ambas as extremidades, como mostrado. Além disso, os comandos frame-relay map não precisam ter o parâmetro broadcast porque os pacotes OSPF são unicast com a instrução neighbor.

Dicas de verificação

Esta é a saída do comando show para o Roteador 1.

Router1# show ip ospf neighbors
      
     Neighbor ID     Pri   State           Dead Time   Address         Interface
     192.0.2.2           1   FULL/BDR        00:01:39    192.0.2.1         Serial2
     
Router1# show ip ospf interface s2
     Serial2 is up, line protocol is up 
       Internet Address 192.0.2.1/24, Area 0 
       Process ID 1, Router ID 192.0.2.3, Network Type NON_BROADCAST, Cost: 64
       Transmit Delay is 1 sec, State DR, Priority 1 
       Designated Router (ID) 192.0.2.3, Interface address 192.0.2.1
       Backup Designated router (ID) 192.0.2.2, Interface address 192.0.2.1
       Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
         Hello due in 00:00:19
       Index 1/1, flood queue length 0
       Next 0x0(0)/0x0(0)
       Last flood scan length is 2, maximum is 2
       Last flood scan time is 0 msec, maximum is 0 msec
       Neighbor Count is 1, Adjacent neighbor count is 1 
         Adjacent with neighbor 192.0.2.2  (Backup Designated Router)
       Suppress hello for 0 neighbor(s)

E a saída para o Roteador 2 é a seguinte:

Router2# show ip ospf neighbor
      
     Neighbor ID     Pri   State           Dead Time   Address         Interface
     192.0.2.3           1   FULL/DR         00:01:49     192.0.2.1         Serial1/0
     
Router2# show ip ospf interface s1/0
     Serial1/0 is up, line protocol is up 
       Internet Address 192.0.2.1/24, Area 0 
       Process ID 1, Router ID 192.0.2.2, Network Type NON_BROADCAST, Cost: 64
       Transmit Delay is 1 sec, State BDR, Priority 1 
       Designated Router (ID) 192.0.2.3, Interface address 192.0.2.1
       Backup Designated router (ID) 192.0.2.2, Interface address 192.0.2.1
       Timer intervals configured, Hello 30, Dead 120, Wait 120, 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 2, maximum is 2
       Last flood scan time is 0 msec, maximum is 0 msec
       Neighbor Count is 1, Adjacent neighbor count is 1 
         Adjacent with neighbor 192.0.2.3  (Designated Router)
       Suppress hello for 0 neighbor(s)

Configurações para ponto a multiponto

interface Loopback0
      ip address 192.0.2.3 255.255.255.255
     !
     interface Serial2
      ip address 192.0.2.1 255.255.255.0
      encapsulation frame-relay
      ip ospf network point-to-multipoint
      no keepalive
      frame-relay map ip 192.0.2.1 16 broadcast
     !
     router ospf 1
      network 192.0.2.0 0.0.0.255 area 0
     !

interface Loopback0
      ip address 192.0.2.2 255.255.255.255
     !
     interface Serial1/0
      ip address 192.0.2.1 255.255.255.0
      encapsulation frame-relay
      ip ospf network point-to-multipoint
      no keepalive
      clockrate 2000000
      frame-relay map ip 192.0.2.1 16 broadcast
     !
     router ospf 1
      network 192.0.2.0 0.0.0.255 area 0

Dicas de verificação

Esta é a saída do comando show para o Roteador 1.

Router1# show ip ospf neighbors
      
     Neighbor ID     Pri   State           Dead Time   Address         Interface
     192.0.2.2           1   FULL/  -        00:01:53    192.0.2.1         Serial2
     
Router1# show ip ospf interface s2
     Serial2 is up, line protocol is up 
       Internet Address 192.0.2.1/24, Area 0 
       Process ID 1, Router ID 192.0.2.3, Network Type POINT_TO_MULTIPOINT, Cost: 64
       Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT,
       Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
         Hello due in 00:00:18
       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 192.0.2.2
       Suppress hello for 0 neighbor(s)

E a saída para o Roteador 2 é a seguinte:

Router2# show ip ospf neighbor
      
     Neighbor ID     Pri   State           Dead Time   Address         Interface
     192.0.2.3           1   FULL/  -        00:01:58     192.0.2.1         Serial1/0

Router2# show ip ospf interface s1/0
     Serial1/0 is up, line protocol is up 
       Internet Address 192.0.2.1/24, Area 0 
       Process ID 1, Router ID 192.0.2.2, Network Type POINT_TO_MULTIPOINT, Cost: 64
       Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT,
       Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
         Hello due in 00:00:18
       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 192.0.2.3
       Suppress hello for 0 neighbor(s)

Observação: não há DR e BDR eleitos quando a rede NBMA é configurada como ponto a multiponto, como mostrado nas saídas, já que ela é tratada como uma coleção de links ponto a ponto.

Para obter mais informações, consulte Configuração do OSPF.

Informações Relacionadas

• Página de suporte de OSPF
• Página de Suporte aos Protocolos de IP Routing
• Suporte Técnico e Documentação - Cisco Systems