一、BGP屬性分類
| 公有必遵 |
Origin（起源屬性） |
IGP（i）、EGP（e）、Incomplete（?） |
| AS-PATH（路徑屬性） |
越短越優(EBGP、IBGP) |
|
| Next-Hop（下一跳屬性） |
/ |
|
| 公認任意 |
Local Pref（本地優先級屬性） |
越大越優(IBGP) |
| 可選過渡 |
Community（社區屬性） |
/ |
| 可選非過渡 |
MED屬性 |
MED值越小越優(EBGP、IBGP) |
二、BGP選路規則
1、若去往目的網絡的路由下一跳不可達，則可以忽略此路由
2、Preferred-Value優先級以數值高的路由優先
3、Local-Preference優先級以數值高的路由優先（默認100）
4、聚合路由優先級高於非聚合路由
5、本地手動聚合路由的優先級高於本地自動聚合的路由
6、本地通過Network命令引入的路由的優先級高於本地通過Import-route命令引入的路由
7、AS路徑長度最短（最少個數）的路徑優先級高
8、比較Origin屬性，IGP優先級高於EGP，EGP優先級高於Incomplete
9、選擇MED優先級較小的路由
10、EBGP路由優先級高於IBGP路由
11、BGP優先選擇到BGP下一跳的IGP度量低的路經
當以上全部相同，則為等價路由，可以負載分擔(注：AS-PATH必須一致)，當負載分擔時，以下3條原則無線
12、比較Cluster-List長度，短者優先
13、比較Originator ID(如果沒有Originator ID，則用Router ID比較)選擇數值較小的路徑
14、比較對等體的IP地址，選擇IP地址數值最小的路徑
三、BGP屬性配置
要求：R1環回到R5 環回從R2走
R5環回到R1 環回從R3走
R1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 g0/0/1
[R1-GigabitEthernet0/0/1]ip add 13.1.1.1 24
[R1-GigabitEthernet0/0/1]undo shutdown
[R1-GigabitEthernet0/0/1]int loop 0
[R1-LoopBack0]ip add 1.1.1.1 32
[R1-LoopBack0]quit
[R1]ip route-static 2.2.2.2 32 12.1.1.2
[R1]ip route-static 3.3.3.3 32 13.1.1.2
[R1]bgp 300
[R1-bgp]router-id 1.1.1.1
[R1-bgp]peer 2.2.2.2 as-number 200
[R1-bgp]peer 2.2.2.2 connect-interface loop 0
[R1-bgp]peer 2.2.2.2 ebgp-max-hop 255
[R1-bgp]peer 3.3.3.3 as-number 200
[R1-bgp]peer 3.3.3.3 connect-interface loop 0
[R1-bgp]peer 3.3.3.3 ebgp-max-hop 255
[R1-bgp]network 1.1.1.1 32
[R1-bgp]network 12.1.1.0 24
[R1-bgp]network 13.1.1.0 24
R2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 23.1.1.0 0.0.0.255
[R2-ospf-1-area-0.0.0.0]quit
[R2-ospf-1]quit
[R2]ip route-static 1.1.1.1 32 12.1.1.1
[R2]bgp 200
[R2-bgp]router-id 2.2.2.2
[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 ebgp-max-hop 255
[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 next-hop-local
[R2-bgp]peer 4.4.4.4 as-number 200
[R2-bgp]peer 4.4.4.4 connect-interface loop 0
[R2-bgp]peer 4.4.4.4 next-hop-local
[R2-bgp]network 1.1.1.1 32
[R2-bgp]network 2.2.2.2 32
[R2-bgp]network 3.3.3.3 32
[R2-bgp]network 4.4.4.4 32
[R2-bgp]network 12.1.1.0 24
[R2-bgp]network 23.1.1.0 24
[R2-bgp]quit
R3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 13.1.1.3 24
[R3-GigabitEthernet0/0/0]undo shutdown
[R3-GigabitEthernet0/0/0]int g0/0/1
[R3-GigabitEthernet0/0/1]ip add 34.1.1.3 24
[R3-GigabitEthernet0/0/1]undo shutdown
[R3-GigabitEthernet0/0/1]int loop 0
[R3-LoopBack0]ip add 3.3.3.3 32
[R3-LoopBack0]quit
[R3]ospf 1 router-id 3.3.3.3
[R3-ospf-1]area 0
[R3-ospf-1-area-0.0.0.0]network 3.3.3.3 0.0.0.0
[R3-ospf-1-area-0.0.0.0]network 34.1.1.0 0.0.0.255
[R3-ospf-1-area-0.0.0.0]quit
[R3-ospf-1]quit
[R3]ip route-static 1.1.1.1 32 13.1.1.1
[R3]bgp 200
[R3-bgp]peer 1.1.1.1 as-number 100
[R3-bgp]peer 1.1.1.1 connect-interface loop 0
[R3-bgp]peer 1.1.1.1 ebgp-max-hop 255
[R3-bgp]peer 2.2.2.2 as-number 200
[R3-bgp]peer 2.2.2.2 connect-interface loop 0
[R3-bgp]peer 2.2.2.2 next-hop-local
[R3-bgp]peer 4.4.4.4 as-number 200
[R3-bgp]peer 4.4.4.4 connect-interface loop 0
[R3-bgp]peer 4.4.4.4 next-hop-local
[R3-bgp]network 1.1.1.1 32
[R3-bgp]network 2.2.2.2 32
[R3-bgp]network 3.3.3.3 32
[R3-bgp]network 4.4.4.4 32
[R3-bgp]network 13.1.1.0 24
[R3-bgp]network 34.1.1.0 24
[R3]acl 2000
[R3-acl-basic-2000]rule permit source 5.5.5.5 0.0.0.0
[R3-acl-basic-2000]quit
[R3]route-policy as permit node 10
[R3-route-policy]if-match acl 2000
[R3-route-policy]apply as-path 222 333 444 additive
[R3-route-policy]quit
[R3]route-policy as permit node 20
[R3-route-policy]quit
[R3]bgp 200
[R3-bgp]peer 1.1.1.1 route-policy as export
[R3-bgp]quit
[R3]quit
<R3>reset bgp all
<R3>system-view
[R3]acl 2001
[R3-acl-basic-2001]rule permit source 1.1.1.1 0.0.0.0
[R3-acl-basic-2001]quit
[R3]route-policy local permit node 10
[R3-route-policy]if-match acl 2001
[R3-route-policy]apply local-preference 200
[R3-route-policy]quit
[R3]route-policy local permit node 20
[R3-route-policy]quit
[R3]bgp 200
[R3-bgp]peer 4.4.4.4 route-policy local export
[R3-bgp]quit
[R3]quit
<R3>reset bgp all
R4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 g0/0/0
[R4-GigabitEthernet0/0/0]ip add 23.1.1.4 24
[R4-GigabitEthernet0/0/0]undo shutdown
[R4-GigabitEthernet0/0/0]int g0/0/1
[R4-GigabitEthernet0/0/1]ip add 34.1.1.4 24
[R4-GigabitEthernet0/0/1]undo shutdown
[R4-GigabitEthernet0/0/1]int g0/0/2
[R4-GigabitEthernet0/0/2]ip add 45.1.1.4 24
[R4-GigabitEthernet0/0/2]undo shutdown
[R4-GigabitEthernet0/0/1]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 23.1.1.0 0.0.0.255
[R4-ospf-1-area-0.0.0.0]network 34.1.1.0 0.0.0.255
[R4-ospf-1-area-0.0.0.0]quit
[R4-ospf-1]quit
[R4]ip route-static 1.1.1.1 32 13.1.1.1
[R4]bgp 200
[R4-bgp]router-id 4.4.4.4
[R4-bgp]peer 2.2.2.2 as-number 200
[R4-bgp]peer 2.2.2.2 connect-interface loop 0
[R4-bgp]peer 2.2.2.2 next-hop-local
[R4-bgp]peer 3.3.3.3 as-number 200
[R4-bgp]peer 3.3.3.3 connect-interface loop 0
[R4-bgp]peer 3.3.3.3 next-hop-local
[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]quit
[R4]ip route-static 5.5.5.5 32 45.1.1.5
[R4]bgp 200
[R4-bgp]network 2.2.2.2 32
[R4-bgp]network 3.3.3.3 32
[R4-bgp]network 4.4.4.4 32
[R4-bgp]network 5.5.5.5 32
[R4-bgp]network 34.1.1.0 24
[R4-bgp]network 23.1.1.0 24
[R4-bgp]network 45.1.1.0 24
R5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]ip route-static 4.4.4.4 32 45.1.1.4
[R5]bgp 300
[R5-bgp]router-id 5.5.5.5
[R5-bgp]peer 4.4.4.4 as-number 200
[R5-bgp]peer 4.4.4.4 connect-interface loop 0
[R5-bgp]peer 4.4.4.4 ebgp-max-hop 255
[R5-bgp]network 5.5.5.5 32
[R5-bgp]network 45.1.1.0 24