BGP协议的原理及应用

一、BGP特征

①　传输协议：TCP，端口号179

②　BGP是外部路由协议，用来在AS之间传递路由信息

③　是一种增强的路径矢量路由协议

④　拥有可靠的路由更新机制

⑤　具备丰富的Metric度量方法

⑥　无环路协议设计

⑦　为路由条目附带多种属性信息

⑧　支持CIDR（无类别域间选路）

⑨　丰富的路由过滤和路由策略

⑩　无需周期性更新

⑪　路由更新时只发增量路由

⑫　周期性发送KeepAlive报文以保持TCP连通性

二、BGP报文

Open报文

Update报文

Notification报文

Router-refresh

KeepAlive

三、BGP状态机

Idle状态

Connect状态

Active状态

OpenSent状态

OpenConfirm状态

Established状态

 

四、BGP数据库

IP路由表（IP-RIB）      IBGP

BGP路由表（Loc-RIB）   EBGP

 

五、BGP对等体配置：对等体交互原则

①从IBGP对等体获得的BGP路由，BGP设备只传递给它的EBGP对等体

②从EBGP对等体获得的BGP路由，BGP设备只传递给它所有EBGP和IBGP对等体（对等体是IBGP只能传一跳，对等体是EBGP则不限制）

③当存在多条到达同一目的地址的有效路由时，BGP设备只将最优路由发布给对等体

④路由更新时，BGP设备只发送更新的BGP路由

⑤所有对等体发送的路由，BGP设备都会接收

⑥所有EBGP对等体在传递过程中下一跳改变

⑦所有IBGP对等体在传递过程中下一跳不变

⑧默认EBGP传递时，TTL值为1

⑨默认IBGP传递时，TTL值为255

六、更新源建立邻居关系

1、BGP直连网段建立邻居

2、BGP环回口建立邻居

①EBGP区域命令

Peer　3.3.3.3　as-number　100　　　　　　　　指向对端BGP

Peer　3.3.3.3　connect-interface　loop back　0　建立邻居接口

Peer　3.3.3.3　ebgp-max-hop　255　　　　修改多跳，默认1跳

设置静态路由下一跳

②IBGP区域命令

Peer　1.1.1.1　as-number　100　　　　　　　　指向对端BGP

Peer　1.1.1.1　connect-interface　loop back　0　建立邻居接口

Peer　1.1.1.1　next-hop-local　　　　下一跳指向自己，此命令只在AS边缘路由器设置

 

1、BGP直连网段建立邻居

 

AR1配置信息

<Huawei>undo terminal monitor

<Huawei>system-view

[Huawei]user-interface console 0

[Huawei-ui-console0]idle-timeout 0 0

[Huawei-ui-console0]sysname R1

[R1]int g0/0/0

[R1-GigabitEthernet0/0/0]ip add 12.1.1.1 24

[R1-GigabitEthernet0/0/0]undo shutdown

[R1-GigabitEthernet0/0/0]int loop 0

[R1-LoopBack0]ip add 1.1.1.1 32

[R1-LoopBack0]quit

[R1]ospf 1

[R1-ospf-1]area 0

[R1-ospf-1-area-0.0.0.0]network 1.1.1.1 0.0.0.0

[R1-ospf-1-area-0.0.0.0]network 12.1.1.0 0.0.0.255

[R1-ospf-1-area-0.0.0.0]quit

[R1-ospf-1]quit

[R1]bgp 100

[R1-bgp]router

[R1-bgp]router-id 1.1.1.1

[R1-bgp]peer 12.1.1.2 as-number 100

[R1-bgp]network 1.1.1.1 32

[R1-bgp]network 12.1.1.0 24

[R1-bgp]display ip rou

AR2配置信息

<Huawei>undo terminal monitor

<Huawei>system-view

[Huawei]user-interface console 0

[Huawei-ui-console0]idle-timeout 0 0

[Huawei-ui-console0]sysname R2

[R2]int g0/0/0

[R2-GigabitEthernet0/0/0]ip add 12.1.1.2 24

[R2-GigabitEthernet0/0/0]undo shutdown

[R2-GigabitEthernet0/0/0]int g0/0/1

[R2-GigabitEthernet0/0/1]ip add 23.1.1.2 24

[R2-GigabitEthernet0/0/1]undo shutdown

[R2-GigabitEthernet0/0/1]int loop 0

[R2-LoopBack0]ip add 2.2.2.2 32

[R2-LoopBack0]quit

[R2]ospf 1

[R2-ospf-1]area 0

[R2-ospf-1-area-0.0.0.0]network 2.2.2.2 0.0.0.0

[R2-ospf-1-area-0.0.0.0]network 12.1.1.0 0.0.0.255

[R2-ospf-1-area-0.0.0.0]quit

[R2-ospf-1]quit

[R2]bgp 100

[R2-bgp]router-id 2.2.2.2

[R2-bgp]peer 12.1.1.1 as-number 100

[R2-bgp]peer 23.1.1.3 as-number 200

[R2-bgp]network 2.2.2.2 32

[R2-bgp]network 12.1.1.0 24

[R2-bgp]network 23.1.1.0 24

[R2-bgp]quit

AR3配置信息

<Huawei>undo terminal monitor

<Huawei>system-view

[Huawei]user-interface console 0

[Huawei-ui-console0]idle-timeout 0 0

[Huawei-ui-console0]sysname R3

[R3]int g0/0/0

[R3-GigabitEthernet0/0/0]ip add 23.1.1.3 24

[R3-GigabitEthernet0/0/0]undo shutdown

[R3-GigabitEthernet0/0/0]int loop 0

[R3-LoopBack0]ip add 3.3.3.3 32

[R3-LoopBack0]quit

[R3]bgp 200

[R3-bgp]router-id 3.3.3.3

[R3-bgp]peer 23.1.1.2 as-number 100

[R3-bgp]quit

[R3]bgp 200

[R3-bgp]network 3.3.3.3 32

[R3-bgp]network 23.1.1.0 24

[R3-bgp]quit

 

2、BGP环回口建立邻居

 

AR5配置信息

<Huawei>undo terminal monitor

<Huawei>system-view

[Huawei]user-interface console 0

[Huawei-ui-console0]idle-timeout 0 0

[Huawei-ui-console0]sysname R5

[R5]int g0/0/0

[R5-GigabitEthernet0/0/0]ip add 45.1.1.5 24

[R5-GigabitEthernet0/0/0]undo shutdown

[R5-GigabitEthernet0/0/0]int loop 0

[R5-LoopBack0]ip add 5.5.5.5 32

[R5-LoopBack0]quit

[R5]bgp 300

[R5-bgp]router-id 5.5.5.5

[R5-bgp]peer 4.4.4.4 as-number 100

[R5-bgp]peer 4.4.4.4 connect-interface loop 0

[R5-bgp]peer 4.4.4.4 ebgp-max-hop 255

[R5-bgp]quit

[R5]ip route-static 4.4.4.4 32 45.1.1.4

[R5]bgp 300

[R5-bgp]network 5.5.5.5 32

[R5-bgp]network 45.1.1.0 24

[R5-bgp]quit

 

AR4配置信息

<Huawei>undo terminal monitor

<Huawei>system-view

[Huawei]user-interface console 0

[Huawei-ui-console0]idle-timeout 0 0

[Huawei-ui-console0]sysname R4

[R4]int g0/0/1

[R4-GigabitEthernet0/0/1]ip add 45.1.1.4 24

[R4-GigabitEthernet0/0/1]undo shutdown

[R4-GigabitEthernet0/0/1]int g0/0/0

[R4-GigabitEthernet0/0/0]ip add 14.1.1.4 24

[R4-GigabitEthernet0/0/0]undo shutdown

[R4-GigabitEthernet0/0/0]int loop 0

[R4-LoopBack0]ip add 4.4.4.4 32

[R4-LoopBack0]quit

[R4]ospf 1 router-id 4.4.4.4

[R4-ospf-1]area 0

[R4-ospf-1-area-0.0.0.0]network 4.4.4.4 0.0.0.0

[R4-ospf-1-area-0.0.0.0]network 14.1.1.0 0.0.0.255

[R4-ospf-1-area-0.0.0.0]quit

[R4-ospf-1]quit

[R4]bgp 100

[R4-bgp]router-id 4.4.4.4

[R4-bgp]peer 5.5.5.5 as-number 300

[R4-bgp]peer 5.5.5.5 connect-interface loop 0

[R4-bgp]peer 5.5.5.5 ebgp-max-hop 255

[R4-bgp]peer 1.1.1.1 as-number 100

[R4-bgp]peer 1.1.1.1 connect-interface loop 0

[R4-bgp]peer 1.1.1.1 next-hop-local

[R4-bgp]peer 2.2.2.2 as-number 100

[R4-bgp]peer 2.2.2.2 connect-interface loop 0

[R4-bgp]peer 2.2.2.2 next-hop-local

[R4-bgp]network 4.4.4.4 32

[R4-bgp]network 45.1.1.0 24

[R4-bgp]network 14.1.1.0 24

[R4-bgp]network 5.5.5.5 32

[R4-bgp]network 1.1.1.1 32

[R4-bgp]network 2.2.2.2 32

AR1配置信息

<Huawei>undo terminal monitor

<Huawei>system-view

[Huawei]user-interface console 0

[Huawei-ui-console0]idle-timeout 0 0

[Huawei-ui-console0]sysname R2

[R2]sysname R1

[R1]int g0/0/1

[R1-GigabitEthernet0/0/1]ip add 14.1.1.1 24

[R1-GigabitEthernet0/0/1]undo shutdown

[R1-GigabitEthernet0/0/1]int g0/0/0

[R1-GigabitEthernet0/0/0]ip add 12.1.1.1 24

[R1-GigabitEthernet0/0/0]undo shutdown

[R1-GigabitEthernet0/0/0]int loop 0

[R1-LoopBack0]ip add 1.1.1.1 32

[R1-LoopBack0]quit

[R1]ospf 1 router-id 1.1.1.1

[R1-ospf-1-area-0.0.0.0]network 1.1.1.1 0.0.0.0

[R1-ospf-1-area-0.0.0.0]network 14.1.1.0 0.0.0.255

[R1-ospf-1-area-0.0.0.0]network 12.1.1.0 0.0.0.255

[R1-ospf-1-area-0.0.0.0]quit

[R1-ospf-1]q

[R1]bgp 100

[R1-bgp]router-id 1.1.1.1

[R1-bgp]peer 4.4.4.4 as-number 100

[R1-bgp]peer 4.4.4.4 connect-interface loop 0

[R1-bgp]peer 2.2.2.2 as-number 100

[R1-bgp]peer 2.2.2.2 connect-interface loop 0

[R1-bgp]network 1.1.1.1 32

[R1-bgp]network 14.1.1.0 24

[R1-bgp]network 12.1.1.0 24

AR2配置信息

<Huawei>undo terminal monitor

<Huawei>system-view

[Huawei]user-interface console 0

[Huawei-ui-console0]idle-timeout 0 0

[Huawei-ui-console0]sysname R2

[R2]int g0/0/0

[R2-GigabitEthernet0/0/0]ip add 12.1.1.2 24

[R2-GigabitEthernet0/0/0]undo shutdown

[R2-GigabitEthernet0/0/0]int g0/0/1

[R2-GigabitEthernet0/0/1]ip add 23.1.1.2 24

[R2-GigabitEthernet0/0/1]undo shutdown

[R2-GigabitEthernet0/0/1]int loop 0

[R2-LoopBack0]ip add 2.2.2.2 32

[R2-LoopBack0]quit

[R2]ospf 1 router-id 2.2.2.2

[R2-ospf-1]area 0

[R2-ospf-1-area-0.0.0.0]network 2.2.2.2 0.0.0.0

[R2-ospf-1-area-0.0.0.0]network 12.1.1.0 0.0.0.255

[R2-ospf-1-area-0.0.0.0]quit

[R2-ospf-1]quit

[R2]bgp 100

[R2-bgp]router-id 2.2.2.2

[R2-bgp]peer 4.4.4.4 as-number 100

[R2-bgp]peer 4.4.4.4 connect-interface loop 0

[R2-bgp]peer 4.4.4.4 next-hop-local

[R2-bgp]peer 1.1.1.1 as-number 100

[R2-bgp]peer 1.1.1.1 connect-interface loop 0

[R2-bgp]peer 1.1.1.1 next-hop-local

[R2-bgp]peer 3.3.3.3 as-number 200

[R2-bgp]peer 3.3.3.3 connect-interface loop 0

[R2-bgp]peer 3.3.3.3 ebgp-max-hop 255

[R2-bgp]quit

[R2]ip route-static 3.3.3.3 32 23.1.1.3

[R2]bgp 100

[R2-bgp]network 2.2.2.2 32

[R2-bgp]network 12.1.1.0 24

[R2-bgp]network 23.1.1.0 24

[R2-bgp]network 3.3.3.3 32

[R2-bgp]network 4.4.4.4 32

AR3配置信息

<Huawei>undo terminal monitor

<Huawei>system-view

[Huawei]user-interface console 0

[Huawei-ui-console0]idle-timeout 0 0

[Huawei-ui-console0]sysname R3

[R3]int g0/0/0

[R3-GigabitEthernet0/0/0]ip add 23.1.1.3 24

[R3-GigabitEthernet0/0/0]undo shutdown

[R3-GigabitEthernet0/0/0]int loop 0

[R3-LoopBack0]ip add 3.3.3.3 32

[R3-LoopBack0]quit

[R3]bgp 200

[R3-bgp]router-id 3.3.3.3

[R3-bgp]peer 2.2.2.2 as-number 100

[R3-bgp]peer 2.2.2.2 connect-interface loop 0

[R3-bgp]peer 2.2.2.2 ebgp-max-hop 255

[R3-bgp]quit

[R3]ip route-static 2.2.2.2 32 23.1.1.2

[R3]bgp 200

[R3-bgp]network 3.3.3.3 32

[R3-bgp]network 23.1.1.0 24

[R3-bgp]quit