配置IPv6 BGP本地首選項功能

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已更新: 2011 年 6 月 15 日
文件 ID:113035

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簡介

本檔案將說明IPv6邊界閘道通訊協定(BGP)Local-Preference功能。本地優先順序是指AS哪條路徑優先退出AS以到達特定網路。具有更高本地優先順序的路徑更優先。優先順序的預設值為100。

必要條件

需求

嘗試此組態之前，請確保符合以下要求：

  • 瞭解BGP路由協定及其操作

  • 瞭解IPv6編址方案

採用元件

本檔案中的資訊已使用以下軟體和硬體版本進行測試

  • Cisco IOS軟體版本12.4，高級IP服務功能集

  • · Cisco 3700系列多重服務存取路由器

慣例

如需文件慣例的詳細資訊，請參閱思科技術提示慣例。

背景資訊

在本例中，路由器R1、R2和R3屬於BGP自治系統編號123。R4屬於自治系統101,R5屬於自治系統100。

三台路由器（R1、R2和R3）配置了OSPFv3以實現IGP連線。所有三台路由器的環回介面Lo 0（1111:111:A::/64 eui-64、222:222:222:A::/64 eui-64和333:333:333:A::/64 eui-64）的IPv6字首在OSPFv3路由協定的區域0中通告。

路由器R1、R2和R3之間通過獲知的環回字首形成IBGP對等。路由器R1和R4通過WAN鏈路（串列連線）連線，形成EBGP對等。同樣，路由器R3和R5正在通過WAN鏈路形成EBGP對等。

路由器R4和R5插入相同的IPv6字首：

  1. 網路BC01:BC1:10:A::/64

  2. 網路BC02:BC1:11:A::/64

  3. 網路BC03:BC1:12:A::/64

由於兩台路由器R4和R5插入了相同的IPv6字首，因此路徑選擇基於BGP已知屬性。在本示例中，選擇了Local Preference。BGP本地優先順序值500通過路由對映為路由器R3上的字首BC01:BC1:10:A::/64設定。這會導致R3成為此字首的退出點，而R1成為其餘兩個字首的退出點。

設定

路由器R1、R2和R3的快速乙太網介面（F0/0和F0/1）啟用了IPv6,IPv6地址格式為eui-64。

網路圖表

本檔案會使用以下網路設定：

ipv6-bgp-local-preference-config-01.gif

組態

本檔案會使用以下設定：

注意：使用ipv6 unicast-routing命令，所有路由器都啟用了IPv6資料包轉發功能。

R1 
interface Loopback0
 no ip address
 ipv6 address 1111:111:111:A::/64 eui-64
 ipv6 enable
 ipv6 ospf 10 area 0

!--- Enables OSPFv3 on the interface and associates !--- the interface loopback0 to area 0.

!
interface FastEthernet0/0
 description CONNECTED TO Rtr2
 no ip address
 duplex auto
 speed auto
 ipv6 address AB01:CD1:123:A::/64 eui-64
 ipv6 enable
 ipv6 ospf 10 area 0
!
interface Serial0/0
 no ip address
 ipv6 address AB01:CD1:123:C::/64 eui-64
 ipv6 enable
 clock rate 2000000
!
interface FastEthernet0/1
 no ip address
 duplex auto
 speed auto
 ipv6 address AB01:CD1:123:B::/64 eui-64
 ipv6 enable
 ipv6 ospf 10 area 0
!
ipv6 router ospf 10
 router-id 1.1.1.1
 log-adjacency-changes
 redistribute connected route-map CONNECTED
!
route-map CONNECTED permit 10
 match interface Serial0/0
!
router bgp 123
 bgp router-id 1.1.1.1
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor 2222:222:222:A:C602:3FF:FEF0:0 remote-as 123
 neighbor 2222:222:222:A:C602:3FF:FEF0:0 update-source Loopback0
 neighbor 3333:333:333:A:C603:3FF:FEF0:0 remote-as 123
 neighbor 3333:333:333:A:C603:3FF:FEF0:0 update-source Loopback0
 neighbor AB01:CD1:123:C:C604:16FF:FE98:0 remote-as 101
 neighbor AB01:CD1:123:C:C604:16FF:FE98:0 ebgp-multihop 5
 !
 address-family ipv6
  neighbor 2222:222:222:A:C602:3FF:FEF0:0 activate
  neighbor 2222:222:222:A:C602:3FF:FEF0:0 next-hop-self
  neighbor 3333:333:333:A:C603:3FF:FEF0:0 activate
  neighbor 3333:333:333:A:C603:3FF:FEF0:0 next-hop-self
  neighbor AB01:CD1:123:C:C604:16FF:FE98:0 activate
 exit-address-family

R2 
interface Loopback0
 no ip address
 ipv6 address 2222:222:222:A::/64 eui-64
 ipv6 enable
 ipv6 ospf 10 area 0
!
interface FastEthernet0/0
 no ip address
 duplex auto
 speed auto
 ipv6 address AB01:CD1:123:A::/64 eui-64
 ipv6 ospf 10 area 0
!
interface FastEthernet0/1
 no ip address
 duplex auto
 speed auto
 ipv6 address AB01:CD1:123:D::/64 eui-64
 ipv6 enable
 ipv6 ospf 10 area 0
!
ipv6 router ospf 10
 router-id 2.2.2.2
 log-adjacency-changes
!
router bgp 123
 no synchronization
 bgp router-id 2.2.2.2
 bgp log-neighbor-changes
 neighbor 1111:111:111:A:C601:3FF:FEF0:0 remote-as 123
 neighbor 1111:111:111:A:C601:3FF:FEF0:0 update-source Loopback0
 neighbor 3333:333:333:A:C603:3FF:FEF0:0 remote-as 123
 neighbor 3333:333:333:A:C603:3FF:FEF0:0 update-source Loopback0
 no auto-summary
 !
 address-family ipv6
  neighbor 1111:111:111:A:C601:3FF:FEF0:0 activate
  neighbor 3333:333:333:A:C603:3FF:FEF0:0 activate
 exit-address-family

R3 
interface Loopback0
 no ip address
 ipv6 address 3333:333:333:A::/64 eui-64
 ipv6 enable
 ipv6 ospf 10 area 0
!
interface FastEthernet0/0
 no ip address
 duplex auto
 speed auto
 ipv6 address AB01:CD1:123:B::/64 eui-64
 ipv6 enable
 ipv6 ospf 10 area 0
!
interface Serial0/0
 no ip address
 ipv6 address AB01:CD1:123:E::/64 eui-64
 ipv6 enable
 clock rate 2000000
!
interface FastEthernet0/1
 no ip address
 duplex auto
 speed auto
 ipv6 address AB01:CD1:123:D::/64 eui-64
 ipv6 ospf 10 area 0
!
ipv6 router ospf 10
 router-id 3.3.3.3
 log-adjacency-changes
 redistribute connected route-map CONNECTED
!
router bgp 123
 no synchronization
 bgp router-id 3.3.3.3
 bgp log-neighbor-changes
 neighbor 1111:111:111:A:C601:3FF:FEF0:0 remote-as 123
 neighbor 1111:111:111:A:C601:3FF:FEF0:0 update-source Loopback0
 neighbor 2222:222:222:A:C602:3FF:FEF0:0 remote-as 123
 neighbor 2222:222:222:A:C602:3FF:FEF0:0 update-source Loopback0
 neighbor AB01:CD1:123:E:C605:16FF:FE98:0 remote-as 202
 neighbor AB01:CD1:123:E:C605:16FF:FE98:0 ebgp-multihop 5
 no auto-summary
 !
 address-family ipv6
  neighbor 1111:111:111:A:C601:3FF:FEF0:0 activate
  neighbor 1111:111:111:A:C601:3FF:FEF0:0 next-hop-self
  neighbor 1111:111:111:A:C601:3FF:FEF0:0 route-map LOCAL_PREF out
  neighbor 2222:222:222:A:C602:3FF:FEF0:0 activate
  neighbor 2222:222:222:A:C602:3FF:FEF0:0 next-hop-self
  neighbor 2222:222:222:A:C602:3FF:FEF0:0 route-map LOCAL_PREF out
  neighbor AB01:CD1:123:E:C605:16FF:FE98:0 activate
 exit-address-family

!
ipv6 prefix-list 10 seq 5 permit BC01:BC1:10:A::/64
!
route-map LOCAL_PREF permit 10
 match ipv6 address prefix-list 10
 set local-preference 500
!
route-map LOCAL_PREF permit 20
!
route-map CONNECTED permit 10
 match interface Serial0/0

R4 
interface Serial0/0
 no ip address
 ipv6 address AB01:CD1:123:C::/64 eui-64
 ipv6 enable
 clock rate 2000000
!
interface Loopback10
 no ip address
 ipv6 address BC01:BC1:10:A::/64 eui-64
 ipv6 enable
!
interface Loopback11
 no ip address
 ipv6 address BC02:BC1:11:A::/64 eui-64
 ipv6 enable
!
interface Loopback12
 no ip address
 ipv6 address BC03:BC1:12:A::/64 eui-64
 ipv6 enable

router bgp 101
 bgp router-id 4.4.4.4
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor AB01:CD1:123:C:C601:3FF:FEF0:0 remote-as 123
 neighbor AB01:CD1:123:C:C601:3FF:FEF0:0 ebgp-multihop 5
 !
 address-family ipv6
  neighbor AB01:CD1:123:C:C601:3FF:FEF0:0 activate
  network BC01:BC1:10:A::/64
  network BC02:BC1:11:A::/64
  network BC03:BC1:12:A::/64
 exit-address-family

R5 
interface Serial0/0
 no ip address
 ipv6 address AB01:CD1:123:E::/64 eui-64
 ipv6 enable
 clock rate 2000000
!
interface Loopback10
 no ip address
 ipv6 address BC01:BC1:10:A::/64 eui-64
 ipv6 enable
!
interface Loopback11
 no ip address
 ipv6 address BC02:BC1:11:A::/64 eui-64
 ipv6 enable
!
interface Loopback12
 no ip address
 ipv6 address BC03:BC1:12:A::/64 eui-64
 ipv6 enable
!
router bgp 202
 bgp router-id 5.5.5.5
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 neighbor AB01:CD1:123:E:C603:3FF:FEF0:0 remote-as 123
 neighbor AB01:CD1:123:E:C603:3FF:FEF0:0 ebgp-multihop 5
 !
 address-family ipv6
  neighbor AB01:CD1:123:E:C603:3FF:FEF0:0 activate
  network BC01:BC1:10:A::/64
  network BC02:BC1:11:A::/64
  network BC03:BC1:12:A::/64
 exit-address-family

驗證

本節提供的資訊可用於確認您的組態是否正常運作。

在路由器R1上

  1. show ipv6 interface brief

    ipv6-bgp-local-preference-config-02.gif

  2. show bgp ipv6 unicast summary

    ipv6-bgp-local-preference-config-03.gif

在路由器R2上

  1. show ipv6 interface brief

    ipv6-bgp-local-preference-config-04.gif

  2. show bgp ipv6 unicast

    注意：未配置Local Preference時，路由器R2(Rtr2)將路由器R1(Rtr1)作為所有已學習IPv6地址的下一跳。 ipv6-bgp-local-preference-config-05.gif

  3. show bgp ipv6 unicast

    為字首BC01:BC1:10:A::/64配置本地首選項500後，R2隻有此字首有不同的出口。

    ipv6-bgp-local-preference-config-06.gif

    注意：字首BC01:BC1:10:A::/64採用路由器R3的退出路徑，因為「本地首選項」設定得更高。

在路由器R3上

  1. show ipv6 interface brief

    ipv6-bgp-local-preference-config-07.gif

  2. show bgp ipv6 unicast summary

    ipv6-bgp-local-preference-config-08.gif

疑難排解

使用這些命令進行故障排除

  1. debug bgp ipv6 updates
  2. clear bgp ipv6 {unicast |組播}

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