🔹类型：外部网关协议 EGP
🔹全称：Border Gateway Protocol
🔹文件：BGP指南-IP单播路由.pdf
🔹视频：BGP基础 - 基本原理
🔹链接：BGP配置

简介

BGP用于在不同的自治系统（AS）之间交换路由信息。当两个AS需要交换路由信息时，每个AS都必须指定一个运行BGP的节点，来代表AS与其他的AS交换路由信息。
BGP属于外部网关路由协议，可以实现自治系统间无环路的域间路由。BGP是沟通Internet广域网的主用路由协议，例如不同省份、不同国家之间的路由大多要依靠BGP协议。BGP可分为 IBGP 和 EBGP。BGP的邻居关系（或称通信对端/对等实体）是通过人工配置实现的，对等实体之间通过TCP会话交互数据。BGP路由器会周期地发送19字节的保持存活keep-alive消息来维护连接。在路由协议中，只有BGP使用TCP作为传输层协议。

IBGP 和 EBGP

  • IBGP：同一个自治系统(AS)中的两个或多个对等实体之间运行的BGP被称为 IBGP（Internal/Interior BGP）
  • EBGP：归属不同的AS的对等实体之间运行的BGP称为 EBGP （External BGP）,用于不同AS间路由信息交换

BGP （边界网关协议） - 图1

交换机 BGP 配置

EBGP 拓扑

image.png

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**

  1. 配置 Router A
  2. -----------------------------------------------------------------------------------------
  3. Switch# configure terminal                                 进入配置模式
  5. Switch(config)# interface eth-0-13                         进入接口模式
  6. Switch(config-if)# no shutdown                             启用端口
  7. Switch(config-if)# no switchport                           将该端口转换为三层interface
  8. Switch(config-if)# ip address 1.1.1.1/24                   配置IP 地址为1.1.1.1/24
  9. Switch(config-if)# exit                                    退出接口模式并且进入配置模式
  11. Switch(config)# interface eth-0-1                          进入接口模式
  12. Switch(config-if)# no shutdown                             启用端口
  13. Switch(config-if)# no switchport                           将该端口转换为三层interface
  14. Switch(config-if)# ip address 2.2.2.1/24                   配置IP 地址为2.2.2.1/24
  15. Switch(config-if)# exit                                    退出接口模式并且进入配置模式
  17. Switch(config)# ip route 3.3.3.0/24 2.2.2.2                增加一条静态路由
  18. Switch(config)# router bgp 100                             创建BGP 100 并进入路由模式
  20. Switch(config-router)# bgp router-id 10.10.10.10           配置BGP router-id
  21. Switch(config-router)# neighbor 1.1.1.2 remote-as 200      配置EBGP 邻居号200
  22. Switch(config)# neighbor 1.1.1.2 ebgp-multihop             配置邻居为ebgp-multihop
  23. Switch(config-router)# network 4.0.0.0/8                   宣告网络号
  24. Switch(config-router)# redistribute static                 重分布静态路由到BGP
  25. Switch(config-router)# redistribute connected              重分布直连路由到BGP
  26. Switch(config-router)# exit                                退出路由模式并且进入配置模式
  29. 配置 Router B
  30. ---------------------------------------------------------------------------------------
  31. Switch# configure terminal                                 进入配置模式
  33. Switch(config)# interface eth-0-13                         进入接口模式
  34. Switch(config-if)# no shutdown                             启用端口
  35. Switch(config-if)# no switchport                           将该端口转换为三层interface
  36. Switch(config-if)# ip address 1.1.1.2/24                   配置IP 地址为1.1.1.2/24
  37. Switch(config-if)# exit                                    退出接口模式并且进入配置模式
  39. Switch(config)# router bgp 200                             创建BGP 200 并进入路由模式
  40. Switch(config-router)# bgp router-id 11.11.11.11           配置BGP router-id
  41. Switch(config-router)# neighbor 1.1.1.1 remote-as 100      配置EBGP 邻居号100
  42. Switch(config)# neighbor 1.1.1.1 ebgp-multihop             配置邻居为ebgp-multihop
  43. Switch(config-router)# redistribute connected              重分布直连路由到BGP
  44. Switch(config-router)# exit                                退出路由模式并且进入配置模式
  48. 试验结果
  49. SwitchA# show ip bgp neighbors
  50. -----------------------------------------------------------------------
  51. BGP neighbor is 1.1.1.2, remote AS 200, local AS 100, external link
  52.   BGP version 4, remote router ID 0.0.0.0
  53.   BGP state = Active
  54.   Last read 00:26:00, hold time is 180, keepalive interval is 60 seconds
  55.   Received 0 messages, 0 notifications, 0 in queue
  56.   Sent 0 messages, 0 notifications, 0 in queue
  57.   Route refresh request: received 0, sent 0
  58.   Minimum time between advertisement runs is 30 seconds
  59.   For address family: IPv4 Unicast
  60.   BGP table version 1, neighbor version 0
  61.   Index 1, Offset 0, Mask 0x2
  62.   0 accepted prefixes
  63.   0 announced prefixes
  64.   Connections established 0; dropped 0
  65.   External BGP neighbor may be up to 255 hops away.
  67. ********Next connect timer due in 87 seconds********
  69. SwitchB# show ip bgp neighbors
  70. ----------------------------------------------------------------------
  71. BGP neighbor is 1.1.1.1, remote AS 100, local AS 200, external link
  72.   BGP version 4, remote router ID 0.0.0.0
  73.   BGP state = Active
  74.   Last read 00:21:39, hold time is 180, keepalive interval is 60 seconds
  75.   Received 0 messages, 0 notifications, 0 in queue
  76.   Sent 0 messages, 0 notifications, 0 in queue
  77.   Route refresh request: received 0, sent 0
  78.   Minimum time between advertisement runs is 30 seconds
  79.   For address family: IPv4 Unicast
  80.   BGP table version 1, neighbor version 0
  81.   Index 1, Offset 0, Mask 0x2
  82.   0 accepted prefixes
  83.   0 announced prefixes
  84.   Connections established 0; dropped 0
  85.   External BGP neighbor may be up to 255 hops away.
  86.   Next connect timer due in 97 seconds


IBGP 拓扑

image.png

image.png

  1. 配置 Router A
  2. -----------------------------------------------------------------------------------------
  3. Switch #configure terminal                                                 进入配置模式                           
  4. Switch (config)# interface eth-0-13                                        进入接口模式                           
  5. Switch (config-if)# no shutdown                                            启用端口                           
  6. Switch (config-if)# no switchport                                          将该端口转换为三层interface                           
  7. Switch (config-if)# ip address 1.1.1.1/24                                  配置IP 地址为1.1.1.1/24                           
  8. Switch (config-if)# exit                                                   退出接口模式并且进入配置模式                           
  9. Switch (config)# interface loopback 0                                      进入接口模式                           
  10. Switch (config-if)# ip address 10.10.10.10/32                              配置IP 地址为10.10.10.10/32                           
  11. Switch (config-if)# exit                                                   退出接口模式并且进入配置模式                           
  12. Switch (config)# ip route 11.11.11.11/32 1.1.1.2                           增加一条静态路由                           
  13. Switch (config)# interface eth-0-1                                         进入接口模式                           
  14. Switch (config-if)# no shutdown                                            启用端                           
  15. Switch (config-if)# no switchport                                          将该端口转换为三层interface                           
  16. Switch (config-if)# ip address 2.2.2.1/24                                  配置IP 地址为2.2.2.1/24                           
  17. Switch (config-if)# exit                                                   退出接口模式并且进入配置模式                           
  18. Switch (config)# ip route 3.3.3.0/24 2.2.2.2                               增加一条静态路由                           
  19. Switch (config)# router bgp 100                                            创建BGP 100 并进入路由模式                           
  20. Switch (config-router)# bgp router-id 10.10.10.10                          配置BGP router-id                           
  21. Switch (config-router)# neighbor 11.11.11.11 remote-as 100                 配置IBGP 邻居AS 号100                           
  22. Switch (config-router)# neighbor 11.11.11.11 update-source loopback 0      配置loopback0 为更新源端口                           
  23. Switch (config-router)# network 4.0.0.0/8                                  宣告网络号                           
  24. Switch (config-router)# redistribute static                                重分布静态路由到BGP                           
  25. Switch (config-router)# redistribute connected                             重分布直连路由到BGP                           
  26. Switch (config-router)# exit                                               退出路由模式并且进入配置模式                           
  29. 配置 Router B
  30. ---------------------------------------------------------------------------------------
  31. Switch #configure terminal                                                 进入配置模式                           
  32. Switch (config)# interface eth-0-13                                        进入接口模式                           
  33. Switch (config-if)# no shutdown                                            启用端口                           
  34. Switch (config-if)# no switchport                                          将该端口转换为三层interface                           
  35. Switch (config-if)# ip address 1.1.1.2/24                                  配置IP 地址为1.1.1.2/24                           
  36. Switch (config-if)# exit                                                   退出接口模式并且进入配置模式                           
  37. Switch (config)# interface loopback 0                                      进入接口模式                           
  38. Switch (config-if)# ip address 11.11.11.11/32                              配置IP 地址为11.11.11.11/32                           
  39. Switch (config-if)# exit                                                   退出接口模式并且进入配置模式                           
  40. Switch (config)# ip route 10.10.10.10/32 1.1.1.1                           增加一条静态路由                           
  41. Switch (config)# router bgp 100                                            创建BGP 100 并进入路由模式                           
  42. Switch (config-router)# bgp router-id 11.11.11.11                          配置BGP router-id                           
  43. Switch (config-router)# neighbor 10.10.10.10 remote-as 100                 配置IBGP 邻居AS 号100                           
  44. Switch (config-router)# neighbor 10.10.10.10 update-source loopback 0      配置loopback0 为更新源端口                           
  45. Switch (config-router)# redistribute connected                             重分布直连路由到BGP                           
  46. Switch (config-router)# exit                                               退出路由模式并且进入配置模式    
  49. 试验结果
  50. SwitchA# show ip bgp neighbors
  51. -----------------------------------------------------------------------
  52. BGP neighbor is 11.11.11.11, remote AS 100, local AS 100, internal link
  53.   BGP version 4, remote router ID 0.0.0.0
  54.   BGP state = Active
  55.   Last read 00:02:32, hold time is 180, keepalive interval is 60 seconds
  56.   Received 0 messages, 0 notifications, 0 in queue
  57.   Sent 0 messages, 0 notifications, 0 in queue
  58.   Route refresh request: received 0, sent 0
  59.   Minimum time between advertisement runs is 5 seconds
  60.   Update source is loopback0
  61.   For address family: IPv4 Unicast
  62.   BGP table version 1, neighbor version 0
  63.   Index 1, Offset 0, Mask 0x2
  64.   0 accepted prefixes
  65.   0 announced prefixes
  66.   Connections established 0; dropped 0
  67.   Next connect timer due in 62 seconds
  69. SwitchB# show ip bgp neighbors
  70. ---------------------------------------------------------------------- 
  71. BGP neighbor is 10.10.10.10, remote AS 100, local AS 100, internal link
  72.   BGP version 4, remote router ID 0.0.0.0
  73.   BGP state = Active
  74.   Last read 00:01:58, hold time is 180, keepalive interval is 60 seconds
  75.   Received 0 messages, 0 notifications, 0 in queue
  76.   Sent 0 messages, 0 notifications, 0 in queue
  77.   Route refresh request: received 0, sent 0
  78.   Minimum time between advertisement runs is 5 seconds
  79.   Update source is loopback0
  80.   For address family: IPv4 Unicast
  81.   BGP table version 1, neighbor version 0
  82.   Index 1, Offset 0, Mask 0x2
  83.   0 accepted prefixes
  84.   0 announced prefixes
  85.   Connections established 0; dropped 0
  86.   Next connect timer due in 17 seconds