Conversão de anúncio de estado de enlace OSPF Not So Stubby Area tipo 7 em tipo 5

Introduction

Este documento mostra como o Open Shortest Path First (OSPF) converte um anúncio link state (LSA) Not So Stubby Area (NSSA) do tipo 7 em um LSA do tipo 5.

Prerequisites

Requirements

Não existem requisitos específicos para este documento.

Componentes Utilizados

Este documento não se restringe a versões de software e hardware específicas.

Conventions

Consulte as Convenções de Dicas Técnicas da Cisco para obter mais informações sobre convenções de documentos.

Configurar

Nesta seção, você encontrará informações para configurar os recursos descritos neste documento.

Observação: para encontrar informações adicionais sobre os comandos usados neste documento, use a ferramenta Command Lookup Tool (somente clientes registrados).

Diagrama de Rede

Este documento utiliza a configuração de rede mostrada neste diagrama.

Configurações

Este documento utiliza as configurações mostradas aqui.

• Router 1.1.1.1

• Router 2.2.2.2

• Router 3.3.3.3

Current configuration:

hostname r1.1.1.1

interface Loopback0
 ip address 1.1.1.1 255.0.0.0

interface Serial2/1/0
 ip address 5.0.0.1 255.0.0.0
  
interface Ethernet2/0/0
 ip address 4.0.0.1 255.0.0.0
 
router ospf 4
 redistribute static metric 5 metric-type 1
 network 5.0.0.0 0.255.255.255 area 1
 network 4.0.0.0 0.255.255.255 area 1
 area 1 nssa
 
ip route 9.0.0.0 255.0.0.0 4.0.0.2

end

Current configuration:

hostname r2.2.2.2

interface Loopback0
 ip address 2.2.2.2 255.0.0.0
 
interface Serial0/1/0
 ip address 5.0.0.2 255.0.0.0

interface ATM1/0.20
 ip address 6.0.0.2 255.0.0.0
 
router ospf 2
 network 5.0.0.0 0.255.255.255 area 1
 network 6.0.0.0 0.255.255.255 area 0
 area 1 nssa

end

Current configuration:

hostname r3.3.3.3

interface Loopback0
 ip address 3.3.3.3 255.0.0.0

interface ATM2/0.20 point-to-point
 ip address 6.0.0.3 255.0.0.0
 
router ospf 2
 network 6.0.0.0 0.255.255.255 area 0

end

Verificar

Esta seção fornece informações que você pode usar para confirmar se sua configuração está funcionando adequadamente.

A Output Interpreter Tool (somente clientes registrados) oferece suporte a determinados comandos show, o que permite exibir uma análise da saída do comando show.

• show ip ospf database —Exibe uma lista dos LSAs e os digita em um banco de dados de estado de link. Esta lista mostra apenas as informações no cabeçalho LSA.

• show ip ospf database nssa-external — Exibe informações somente sobre os LSAs externos de NSSA.

• show ip ospf database external — Exibe informações somente sobre os LSAs externos.

• show ip ospf database [router] [link-state-id] — Exibe uma lista de todos os LSAs de um roteador no banco de dados. Os LSAs são produzidos por cada roteador, e esses LSAs fundamentais listam todos os links, ou interfaces dos roteadores, juntamente com os estados e os custos de saída dos links. Eles são inundados apenas na área de origem.

• show ip ospf database summary <link-state id> — Exibe os links de resumo do roteador de borda de área (ABR).

• show ip route —Exibe o status atual da tabela de roteamento.

Examinar o Banco de Dados OSPF

Para ver como o banco de dados do OSPF parece, considerando esse ambiente de rede, use o comando show ip ospf database.

r2.2.2.2#show ip ospf database 

       OSPF Router with ID (2.2.2.2) (Process ID 2) 

                Router Link States (Area 0) 

Link ID   ADV Router    Age    Seq#           Checksum     Link count 
2.2.2.2    2.2.2.2      1235   0x8000001D     0xD9FF           2 
3.3.3.3    3.3.3.3      1100   0x8000000B     0x9455           2 

                Summary Net Link States (Area 0) 

Link ID   ADV Router   Age    Seq#          Checksum 
4.0.0.0    2.2.2.2     1979   0x80000002    0xFDE7 
5.0.0.0    2.2.2.2     1483   0x80000004    0x8864 

                Router Link States (Area 1) 

Link ID   ADV Router   Age    Seq#          Checksum     Link count 
1.1.1.1    1.1.1.1     319    0x8000000C    0xAFA8           3 
2.2.2.2    2.2.2.2     220    0x8000002F    0xD478           2 

                Summary Net Link States (Area 1) 

Link ID   ADV Router   Age    Seq#           Checksum 
6.0.0.0    2.2.2.2     1483   0x8000001C     0x7894 

                Type-7 AS External Link States (Area 1) 

Link ID   ADV Router   Age    Seq#          Checksum     Tag 
9.0.0.0    1.1.1.1     334    0x80000005    0xD738        0 

                Type-5 AS External Link States 

Link ID   ADV Router   Age    Seq#          Checksum     Tag 
9.0.0.0    2.2.2.2     1725   0x80000004    0x50C6        0 

Para anunciar rotas externas para um NSSA, o Roteador de Limite de Sistema Autônomo (ASBR) cria LSAs externos à NSSA (tipo 7).

r2.2.2.2#show ip ospf database nssa-external 9.0.0.0 

       OSPF Router with ID (2.2.2.2) (Process ID 2) 

                Type-7 AS External Link States (Area 1) 

  Routing Bit Set on this LSA 
  LS age: 381 
  Options: (No TOS-capability, Type 7/5 translation, DC)

!--- This can be translated into a type 5 LSA by !--- an ABR. 

  LS Type: AS External Link 
  Link State ID: 9.0.0.0 (External Network Number ) 

!--- The ASBR (Router 1.1.1.1) advertises !--- 9.0.0.0/8. 

  Advertising Router: 1.1.1.1

!--- Router ID of the ASBR.
 
  LS Seq Number: 80000005 
  Checksum: 0xD738 
  Length: 36 
  Network Mask: /8 
        Metric Type: 1 (Comparable directly to link state metric) 
        TOS: 0 
        Metric: 5 
        Forward Address: 4.0.0.1

!--- Forwarding address is incorrectly specified !--- as an interface on the ASBR.
 

O ABR converte LSAs tipo 7 em LSAs tipo 5 e propaga os LSAs tipo 5 em áreas normais.

r2.2.2.2#show ip ospf database external 9.0.0.0 

       OSPF Router with ID (2.2.2.2) (Process ID 2) 

                Type-5 AS External Link States 

  LS age: 1782 
  Options: (No TOS-capability, DC) 
  LS Type: AS External Link 
  Link State ID: 9.0.0.0 (External Network Number )

!--- Router 2.2.2.2 advertises 9.0.0.0/8.
 
  Advertising Router: 2.2.2.2 

!--- When the conversion is complete, the advertising !--- router ID becomes the ABR router ID !--- because the ABR originates this type 5 LSA. 

  LS Seq Number: 80000004 
  Checksum: 0x50C6 
  Length: 36 
  Network Mask: /8 
        Metric Type: 1 (Comparable directly to link state metric) 
        TOS: 0 
        Metric: 5 
        Forward Address: 4.0.0.1 
        External Route Tag: 0 
  

r2.2.2.2#show ip ospf database router 1.1.1.1 

       OSPF Router with ID (2.2.2.2) (Process ID 2) 

                Router Link States (Area 1) 

  Routing Bit Set on this LSA 
  LS age: 426 
  Options: (No TOS-capability, DC) 
  LS Type: Router Links 
  Link State ID: 1.1.1.1

!--- For router links, Link State ID is always the same !--- as the advertising router (next line). 

  Advertising Router: 1.1.1.1
  LS Seq Number: 8000000C 
  Checksum: 0xAFA8 
  Length: 60 
  AS Boundary Router

!--- Bit E in the router LSA indicates that this router !--- originates from external LSAs.
 
   Number of Links: 3

!--- There are three links in area 1. 


    Link connected to: a Stub Network

!--- This represents the Ethernet segment 4.0.0.0/8.
 
     (Link ID) Network/subnet number: 4.0.0.0 
     (Link Data) Network Mask: 255.0.0.0 
      Number of TOS metrics: 0 
       TOS 0 Metrics: 10

!--- The OSPF cost of the Ethernet segment.
 

    Link connected to: another Router (point-to-point) 

!--- Shows that Router 1.1.1.1 is a neighbor with !--- Router 2.2.2.2. 

     (Link ID) Neighboring Router ID: 2.2.2.2 
     (Link Data) Router Interface address: 5.0.0.1

!--- The interface address that connects to Router !--- 2.2.2.2 is 5.0.0.1.
 
      Number of TOS metrics: 0 
       TOS 0 Metrics: 64

!--- The OSPF cost of the link that connects !--- the two routers.

    Link connected to: a Stub Network 

!--- This represents the serial link 5.0.0.0/8.
 
     (Link ID) Network/subnet number: 5.0.0.0 
     (Link Data) Network Mask: 255.0.0.0 
      Number of TOS metrics: 0 
       TOS 0 Metrics: 64

!--- The OSPF cost of the serial link.

Você pode ver na saída em negrito aqui que, embora o Roteador 2.2.2.2 não tenha nenhuma instrução redistribute em sua configuração, ele ainda é um ASBR porque converte LSAs tipo 7 em LSAs tipo 5.

r2.2.2.2#show ip ospf database router 2.2.2.2 

       OSPF Router with ID (2.2.2.2) (Process ID 2) 

                Router Link States (Area 0) 

  LS age: 1361 
  Options: (No TOS-capability, DC) 
  LS Type: Router Links 
  Link State ID: 2.2.2.2 
  Advertising Router: 2.2.2.2 
  LS Seq Number: 8000001D 
  Checksum: 0xD9FF 
  Length: 48 
  Area Border Router 
  
!--- Bit B is set in the router LSA to indicate !--- that this router is an ABR.
 
  AS Boundary Router
  
!--- Bit E in the router LSA indicates that this router !--- originates from external LSAs.

   Number of Links: 2 
  
!--- There are two links in area 0. 


    Link connected to: another Router (point-to-point) 
     (Link ID) Neighboring Router ID: 3.3.3.3 
     (Link Data) Router Interface address: 6.0.0.2 
      Number of TOS metrics: 0 
       TOS 0 Metrics: 1 

    Link connected to: a Stub Network 
     (Link ID) Network/subnet number: 6.0.0.0 
     (Link Data) Network Mask: 255.0.0.0 
      Number of TOS metrics: 0 
       TOS 0 Metrics: 1

                Router Link States (Area 1) 

  LS age: 346 
  Options: (No TOS-capability, DC) 
  LS Type: Router Links 
  Link State ID: 2.2.2.2 
  Advertising Router: 2.2.2.2 
  LS Seq Number: 8000002F 
  Checksum: 0xD478 
  Length: 48 
  Area Border Router 
  AS Boundary Router 
   Number of Links: 2 

    Link connected to: another Router (point-to-point) 
     (Link ID) Neighboring Router ID: 1.1.1.1 
     (Link Data) Router Interface address: 5.0.0.2 
      Number of TOS metrics: 0 
       TOS 0 Metrics: 64 

    Link connected to: a Stub Network 
     (Link ID) Network/subnet number: 5.0.0.0 
     (Link Data) Network Mask: 255.0.0.0 
      Number of TOS metrics: 0 
       TOS 0 Metrics: 64 
  

r2.2.2.2#show ip ospf database router 3.3.3.3 

       OSPF Router with ID (2.2.2.2) (Process ID 2) 

                Router Link States (Area 0) 

  LS age: 1245 
  Options: (No TOS-capability, DC) 
  LS Type: Router Links 
  Link State ID: 3.3.3.3 
  Advertising Router: 3.3.3.3 
  LS Seq Number: 8000000B 
  Checksum: 0x9455 
  Length: 48 
   Number of Links: 2 

    Link connected to: another Router (point-to-point) 
     (Link ID) Neighboring Router ID: 2.2.2.2 
     (Link Data) Router Interface address: 6.0.0.3 
      Number of TOS metrics: 0 
       TOS 0 Metrics: 1 

    Link connected to: a Stub Network 
     (Link ID) Network/subnet number: 6.0.0.0 
     (Link Data) Network Mask: 255.0.0.0 
      Number of TOS metrics: 0 
       TOS 0 Metrics: 1 

Para anunciar rotas de uma área para outra, o ABR cria LSAs de resumo (tipo 3).

r2.2.2.2#show ip ospf database summary 4.0.0.0 

       OSPF Router with ID (2.2.2.2) (Process ID 2) 

                Summary Net Link States (Area 0) 

  LS age: 172 
  Options: (No TOS-capability, DC) 
  LS Type: Summary Links(Network) 
  Link State ID: 4.0.0.0 (summary Network Number)
  
!--- The ABR (Router 2.2.2.2) advertises !--- 4.0.0.0/8 into area 0.

  Advertising Router: 2.2.2.2 
  LS Seq Number: 80000003 
  Checksum: 0xFBE8 
  Length: 28 
  Network Mask: /8 
        TOS: 0  Metric: 74 

r2.2.2.2#show ip ospf database summary 5.0.0.0 

       OSPF Router with ID (2.2.2.2) (Process ID 2) 

                Summary Net Link States (Area 0) 

  LS age: 1687 
  Options: (No TOS-capability, DC) 
  LS Type: Summary Links(Network) 
  Link State ID: 5.0.0.0 (summary Network Number)
  
!--- The ABR (Router 2.2.2.2) advertises !--- 5.0.0.0/8 into area 0. 

  Advertising Router: 2.2.2.2 
  LS Seq Number: 80000004 
  Checksum: 0x8864 
  Length: 28 
  Network Mask: /8 
        TOS: 0  Metric: 64 

r2.2.2.2#show ip ospf database summary 6.0.0.0 

       OSPF Router with ID (2.2.2.2) (Process ID 2) 

                Summary Net Link States (Area 1) 

  LS age: 1697 
  Options: (No TOS-capability, DC) 
  LS Type: Summary Links(Network) 
  Link State ID: 6.0.0.0 (summary Network Number)
  
!--- The ABR (Router 2.2.2.2) advertises !--- 6.0.0.0/8 into area 1.

  Advertising Router: 2.2.2.2 
  LS Seq Number: 8000001C 
  Checksum: 0x7894 
  Length: 28 
  Network Mask: /8 
        TOS: 0  Metric: 1 

Os LSAs de resumo do ASBR não são necessários nesse caso porque o ABR origina o LSA externo e o ABR pode ser alcançado na área 0. Compare esse exemplo com um cenário no qual a NSSA era uma área normal, observando o exemplo de banco de dados How OSPF Propagates External Routes into Multiple Areas (Como o OSPF propaga as rotas externas em múltiplas áreas).

Esta saída da tabela de roteamento mostra os diferentes tipos de rotas OSPF que a 9.0.0.0 é conhecida por cada roteador.

r1.1.1.1#show ip route 9.0.0.0 
Routing entry for 9.0.0.0/8 
  Known via "static", distance 1, metric 0 
  Redistributing via ospf 4 
  Advertised by ospf 4 metric 5 metric-type 1 
  Routing Descriptor Blocks: 
  * 4.0.0.2 
      Route metric is 0, traffic share count is 1

r2.2.2.2#show ip route ospf 
O    4.0.0.0/8 [110/74] via 5.0.0.1, 01:10:13, Serial0/1/0 
O N1 9.0.0.0/8 [110/79] via 5.0.0.1, 01:07:20, Serial0/1/0 

R3.3.3.3#show ip route ospf
O IA 4.0.0.0/8 [110/75] via 6.0.0.2, 02:11:14, ATM2/0.20 
O IA 5.0.0.0/8 [110/65] via 6.0.0.2, 03:10:41, ATM2/0.20 
O E1 9.0.0.0/8 [110/80] via 6.0.0.2, 02:08:11, ATM2/0.20 

Troubleshoot

Atualmente, não existem informações disponíveis específicas sobre Troubleshooting para esta configuração.

Informações Relacionadas

• Como o OSPF propaga as rotas externas em áreas múltiplas
• Manual de explicações do banco de dados OSPF
• Suporte à tecnologia OSPF
• Página de Suporte do IP Routing
• Suporte Técnico e Documentação - Cisco Systems