7.6 BGP路由优选规则-大赛人网

7.优选MED属性值最小的路由

1）基本配置同上，修改MED属性

[R2]ip ip-prefix 1 index 10 permit 2.2.2.2 32
[R2]route-policy dsrw.com permit node 10  
[R2-route-policy]if-match ip-prefix 1
[R2-route-policy]apply  cost 1000 
[R2]bgp 200
[R2-bgp]peer 12.1.1.1 route-policy dsrw.com export

2）查看路由表

<R1>display bgp routing-table 2.2.2.2
 BGP local router ID : 12.1.1.1
 Local AS number : 13
 Paths:   2 available, 1 best, 1 select
 BGP routing table entry information of 2.2.2.2/32:
 From: 3.3.3.3 (3.3.3.3)
 Route Duration: 00h47m08s  
 Relay IP Nexthop: 13.1.1.3
 Relay IP Out-Interface: GigabitEthernet0/0/2
 Original nexthop: 3.3.3.3
 Qos information : 0x0
 AS-path 200, origin igp, MED 0, localpref 100, pref-val 0, valid, internal, best, select, active, pre 255, IGP cost 1
 Advertised to such 1 peers:
    12.1.1.2
 BGP routing table entry information of 2.2.2.2/32:
 From: 12.1.1.2 (2.2.2.2)
 Route Duration: 00h01m15s  
 Direct Out-interface: GigabitEthernet0/0/0
 Original nexthop: 12.1.1.2
 Qos information : 0x0
 AS-path 200, origin igp, MED 1000, pref-val 0, valid, external, pre 255, not preferred for MED
 Not advertised to any peer yet

8.优选从EBGP对等体学来的路由（EBGP路由优先级高于IBGP路由）

图片[2]-7.6 BGP路由优选规则-大赛人网 — 图7-15 优选从EBGP对等体学来的路由

1）基本配置

[R1]ospf 1 router-id 1.1.1.1
[R1-ospf-1]area 0
[R1-ospf-1-area-0.0.0.0]network 13.1.1.0 0.255.255.255
[R1-ospf-1-area-0.0.0.0]network 1.1.1.1 0.0.0.0

[R3]ospf 1 router-id 3.3.3.3
[R3-ospf-1]area 0
[R3-ospf-1-area-0.0.0.0]network 13.1.1.0 0.255.255.255
[R3-ospf-1-area-0.0.0.0]network 3.3.3.3 0.0.0.0

2）配置BGP

[R1]bgp 13
[R1-bgp]router-id 1.1.1.1
[R1-bgp]peer 3.3.3.3 as-number 13
[R1-bgp]peer 3.3.3.3 connect-interface LoopBack 0
[R1-bgp]peer 3.3.3.3 next-hop-local
[R1-bgp]peer 12.1.1.2 as-number 200

[R2]bgp 200
[R2-bgp]router-id 2.2.2.2
[R2-bgp]peer 12.1.1.1 as-number 13
[R2-bgp]peer 23.1.1.3 as-number 13
[R2-bgp]network 2.2.2.2 32

[R3]bgp 13
[R3-bgp]router-id 3.3.3.3
[R3-bgp]peer 1.1.1.1 as-number 13
[R3-bgp]peer 1.1.1.1 connect-interface  LoopBack 0
[R3-bgp]peer 1.1.1.1 next-hop-local
[R3-bgp]peer 23.1.1.2 as-number 200

3）查看BGP路由表，EBGP通告优于IBGP

<R1>dis bgp routing-table 
Total Number of Routes: 2
      Network            NextHop        MED        LocPrf    PrefVal Path/Ogn
*>   2.2.2.2/32         12.1.1.2        0                     0      200i
 * i                     3.3.3.3         0          100        0      200i
<R1>dis bgp routing-table 2.2.2.2
 BGP local router ID : 12.1.1.1
 Local AS number : 13
 Paths:   2 available, 1 best, 1 select
 BGP routing table entry information of 2.2.2.2/32:
 From: 12.1.1.2 (2.2.2.2)
 Route Duration: 00h01m00s  
 Direct Out-interface: GigabitEthernet0/0/0
 Original nexthop: 12.1.1.2
 Qos information : 0x0
 AS-path 200, origin igp, MED 0, pref-val 0, valid, external, best, select, active, pre 255
 Advertised to such 1 peers:
    3.3.3.3
 BGP routing table entry information of 2.2.2.2/32:
 From: 3.3.3.3 (3.3.3.3)
 Route Duration: 00h52m18s  
 Relay IP Nexthop: 13.1.1.3
 Relay IP Out-Interface: GigabitEthernet0/0/2
 Original nexthop: 3.3.3.3
 Qos information : 0x0
 AS-path 200, origin igp, MED 0, localpref 100, pref-val 0, valid, internal, pre 255, IGP cost 1, not preferred for peer type
 Not advertised to any peer yet

9.优选Next_Hop的IGP度量值最小的路由

图片[3]-7.6 BGP路由优选规则-大赛人网 — 图7-16 优选Next_Hop的IGP度量值最小的路由网络拓扑

1）基本配置

[R2]ospf 1 router-id 2.2.2.2
[R2-ospf-1]area 0
[R2-ospf-1-area-0.0.0.0]network 24.1.1.0 0.255.255.255
[R2-ospf-1-area-0.0.0.0]network 2.2.2.2 0.0.0.0

[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 0.255.255.255

[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 34.1.1.0 0.255.255.255

[R4-ospf-1-area-0.0.0.0]network 24.1.1.0 0.255.255.255

2）BGP配置

[R1]bgp 100
[R1-bgp]peer 12.1.1.2 as-number 234
[R1-bgp]peer 13.1.1.3 as-number 234
[R1-bgp]network 1.1.1.1 32

[R2]bgp 234
[R2-bgp]peer 4.4.4.4 as-number 234
[R2-bgp]peer 4.4.4.4 connect-interface LoopBack 0
[R2-bgp]peer 4.4.4.4 next-hop-local
[R2-bgp]peer 12.1.1.1 as-number 100

[R3]bgp 234
[R3-bgp]peer 4.4.4.4 as-number 234
[R3-bgp]peer 4.4.4.4 connect-interface  LoopBack 0
[R3-bgp]peer 4.4.4.4 next-hop-local
[R3-bgp]peer 13.1.1.1 as-number 100

[R4]bgp 234
[R4-bgp]peer 2.2.2.2 as-number 234
[R4-bgp]peer 2.2.2.2 connect-interface LoopBack 0
[R4-bgp]peer 3.3.3.3 as-number 234
[R4-bgp]peer 3.3.3.3 connect-interface LoopBack 0

3）查看BGP路由表

[R4-bgp]display  bgp routing-table 
Network            NextHop        MED        LocPrf    PrefVal Path/Ogn
*>i  1.1.1.1/32         2.2.2.2         0          100        0      100i
* i                     3.3.3.3         0          100        0      100i

[R4-bgp]display bgp routing-table 1.1.1.1
 BGP local router ID : 4.4.4.4
 Local AS number : 234
 Paths:   2 available, 1 best, 1 select
 BGP routing table entry information of 1.1.1.1/32:
 From: 2.2.2.2 (2.2.2.2)
 Route Duration: 00h06m49s  
 Relay IP Nexthop: 24.1.1.2
 Relay IP Out-Interface: GigabitEthernet0/0/1
 Original nexthop: 2.2.2.2
 Qos information : 0x0
 AS-path 100, origin igp, MED 0, localpref 100, pref-val 0, valid, internal, best, select, active, pre 255, IGP cost 1
 Not advertised to any peer yet

 BGP routing table entry information of 1.1.1.1/32:
 From: 3.3.3.3 (34.1.1.3)
 Route Duration: 00h06m40s  
 Relay IP Nexthop: 34.1.1.3
 Relay IP Out-Interface: GigabitEthernet0/0/0
 Original nexthop: 3.3.3.3
 Qos information : 0x0
 AS-path 100, origin igp, MED 0, localpref 100, pref-val 0, valid, internal, pre 255, IGP cost 1, not preferred for router ID
 Not advertised to any peer yet

4）修改R2的lo接口COST值，查看R4的BGP路由表

[R2]interface LoopBack 0
[R2-LoopBack0]ospf cost 9

<R4>dis bgp routing-table 
Network            NextHop        MED        LocPrf    PrefVal Path/Ogn
*>i  1.1.1.1/32         3.3.3.3         0          100        0      100i
* i                     2.2.2.2         0          100        0      100i


<R4>dis bgp routing-table 1.1.1.1

 BGP local router ID : 4.4.4.4
 Local AS number : 234
 Paths:   2 available, 1 best, 1 select
 BGP routing table entry information of 1.1.1.1/32:
 From: 3.3.3.3 (34.1.1.3)
 Route Duration: 00h12m37s  
 Relay IP Nexthop: 34.1.1.3
 Relay IP Out-Interface: GigabitEthernet0/0/0
 Original nexthop: 3.3.3.3
 Qos information : 0x0
 AS-path 100, origin igp, MED 0, localpref 100, pref-val 0, valid, internal, best, select, active, pre 255, IGP cost 1
 Not advertised to any peer yet
 BGP routing table entry information of 1.1.1.1/32:
 From: 2.2.2.2 (2.2.2.2)
 Route Duration: 00h12m46s  
 Relay IP Nexthop: 24.1.1.2
 Relay IP Out-Interface: GigabitEthernet0/0/1
 Original nexthop: 2.2.2.2
 Qos information : 0x0
 AS-path 100, origin igp, MED 0, localpref 100, pref-val 0, valid, internal, pre 255, IGP cost 10, not preferred for IGP cost
 Not advertised to any peer yet

10.优选Cluster_List最短的路由

图片[4]-7.6 BGP路由优选规则-大赛人网 — 图7-17 优选Cluster_List最短的路由网络拓扑

1）基本配置

[R1]ospf 1 router-id 1.1.1.1
[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 0.255.255.255
[R1-ospf-1-area-0.0.0.0]network 13.1.1.0 0.255.255.255

[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 0.255.255.255
[R2-ospf-1-area-0.0.0.0]network 25.1.1.0 0.255.255.255

[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 13.1.1.0 0.255.255.255
[R3-ospf-1-area-0.0.0.0]network 34.1.1.0 0.255.255.255

[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 34.1.1.0 0.255.255.255
[R4-ospf-1-area-0.0.0.0]network 45.1.1.0 0.255.255.255

[R5]ospf 1 router-id 5.5.5.5
[R5-ospf-1]area 0
[R5-ospf-1-area-0.0.0.0]network 5.5.5.5 0.0.0.0
[R5-ospf-1-area-0.0.0.0]network 25.1.1.0 0.255.255.255
[R5-ospf-1-area-0.0.0.0]network 45.1.1.0 0.255.255.255

2)创建GBP

[R1]bgp 12345
[R1-bgp]peer 2.2.2.2 as-number 12345
[R1-bgp]peer 2.2.2.2 connect-interface LoopBack 0
[R1-bgp]peer 3.3.3.3 as-number 12345
[R1-bgp]peer 3.3.3.3 connect-interface LoopBack 0
[R1-bgp]network 11.11.11.11 32

[R2]bgp 12345
[R2-bgp]peer 1.1.1.1 as-number 12345
[R2-bgp]peer 1.1.1.1 connect-interface LoopBack 0
[R2-bgp]peer 5.5.5.5 as-number 12345 
[R2-bgp]peer 5.5.5.5 connect-interface LoopBack 0
[R2-bgp]peer 1.1.1.1 reflect-client

[R3]bgp 12345
[R3-bgp]peer 1.1.1.1 as-number 12345
[R3-bgp]peer 1.1.1.1 connect-interface LoopBack 0
[R3-bgp]peer 4.4.4.4 as-number 12345
[R3-bgp]peer 4.4.4.4 connect-interface LoopBack 0
[R3-bgp]peer 1.1.1.1 reflect-client

[R4]bgp 12345
[R4-bgp]peer 3.3.3.3 as-number 12345
[R4-bgp]peer 3.3.3.3 connect-interface LoopBack 0
[R4-bgp]peer 5.5.5.5 as-number 12345
[R4-bgp]peer 5.5.5.5 connect-interface LoopBack 0
[R4-bgp]peer 3.3.3.3 reflect-client

[R5]bgp 12345
[R5-bgp]peer 2.2.2.2 as-number 12345
[R5-bgp]peer 2.2.2.2 connect-interface LoopBack 0
[R5-bgp]peer 4.4.4.4 as-number 12345
[R5-bgp]peer 4.4.4.4 connect-interface LoopBack 0

3）查看BGP路由表

[R5]display bgp routing-table
Network            NextHop        MED        LocPrf    PrefVal Path/Ogn
*>i  11.11.11.11/32     1.1.1.1         0          100        0      i
* i                     1.1.1.1         0          100        0      i

[R5]display bgp routing-table 11.11.11.11
 BGP local router ID : 45.1.1.5
 Local AS number : 12345
 Paths:   2 available, 1 best, 1 select
 BGP routing table entry information of 11.11.11.11/32:
 From: 2.2.2.2 (2.2.2.2)
 Route Duration: 00h01m20s  
 Relay IP Nexthop: 25.1.1.2
 Relay IP Out-Interface: GigabitEthernet0/0/2
 Original nexthop: 1.1.1.1
 Qos information : 0x0
 AS-path Nil, origin igp, MED 0, localpref 100, pref-val 0, valid, internal, best, select, active, pre 255, IGP cost 2
 Originator:  1.1.1.1
 Cluster list: 2.2.2.2
 Not advertised to any peer yet

 BGP routing table entry information of 11.11.11.11/32:
 From: 4.4.4.4 (4.4.4.4)
 Route Duration: 00h01m20s  
 Relay IP Nexthop: 25.1.1.2
 Relay IP Out-Interface: GigabitEthernet0/0/2
 Original nexthop: 1.1.1.1
 Qos information : 0x0
 AS-path Nil, origin igp, MED 0, localpref 100, pref-val 0, valid, internal, pre 255, IGP cost 2, not preferred for Cluster List
 Originator:  1.1.1.1
 Cluster list: 4.4.4.4, 3.3.3.3
 Not advertised to any peer yet

11.优选Router-ID最小的设备通过的路由

图片[5]-7.6 BGP路由优选规则-大赛人网 — 图7-18 优选Router-ID最小的设备通过的路由网络拓扑

1）基本配置

[R1]ospf 1 router-id 1.1.1.1
[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 0.255.255.255
[R1-ospf-1-area-0.0.0.0]network 13.1.1.0 0.255.255.255 

[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 0.255.255.255

[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 13.1.1.0 0.255.255.255

2）配置BGP

[R1]bgp 123
[R1-bgp]router-id 1.1.1.1
[R1-bgp]peer 2.2.2.2 as-number 123
[R1-bgp]peer 2.2.2.2 connect-interface LoopBack 0
[R1-bgp]peer 3.3.3.3 as-number 123
[R1-bgp]peer 3.3.3.3 connect-interface LoopBack 0
[R1-bgp]network 11.11.11.11 32

[R2]bgp 123
[R2-bgp]router-id 2.2.2.2
[R2-bgp]peer 1.1.1.1 as-number 123
[R2-bgp]peer 1.1.1.1 connect-interface LoopBack 0
[R2-bgp]peer 1.1.1.1 next-hop-local
[R2-bgp]peer 24.1.1.4 as-number 400

[R3]bgp 123
[R3-bgp]router-id 3.3.3.3
[R3-bgp]peer 1.1.1.1 as-number 123
[R3-bgp]peer 1.1.1.1 connect-interface LoopBack 0
[R3-bgp]peer 1.1.1.1 next-hop-local
[R3-bgp]peer 34.1.1.4 as
[R3-bgp]peer 34.1.1.4 as-number 400

[R4]bgp 400
[R4-bgp]router-id 4.4.4.4
[R4-bgp]peer 24.1.1.2 as-number 123
[R4-bgp]peer 34.1.1.3 as-number 123

2）查看BGP路由表

<R4>dis bgp routing-table 
Network            NextHop        MED        LocPrf    PrefVal Path/Ogn
*>   11.11.11.11/32     24.1.1.2                              0      123i
*                       34.1.1.3                              0      123i

[R4]display bgp routing-table 11.11.11.11
 BGP local router ID : 4.4.4.4
 Local AS number : 400
 Paths:   2 available, 1 best, 1 select
 BGP routing table entry information of 11.11.11.11/32:
 From: 24.1.1.2 (2.2.2.2)
 Route Duration: 00h01m27s  
 Direct Out-interface: GigabitEthernet0/0/1
 Original nexthop: 24.1.1.2
 Qos information : 0x0
 AS-path 123, origin igp, pref-val 0, valid, external, best, select, active, pre 255
 Advertised to such 2 peers:
    34.1.1.3
    24.1.1.2
 BGP routing table entry information of 11.11.11.11/32:
 From: 34.1.1.3 (3.3.3.3)
 Route Duration: 00h03m37s  
 Direct Out-interface: GigabitEthernet0/0/0
 Original nexthop: 34.1.1.3
 Qos information : 0x0
 AS-path 123, origin igp, pref-val 0, valid, external, pre 255, not preferred for router ID
 Not advertised to any peer yet

12.优选具有最小IP地址的对等体通告的路由

图片[6]-7.6 BGP路由优选规则-大赛人网 — 图7-19 优选具有最小IP地址的对等体通告的路由网络拓扑

1）配置BGP

[R1]bgp 100
[R1-bgp]peer 12.1.1.2 as-number 200
[R1-bgp]peer 21.1.1.2  as-number 200
[R1-bgp]network 1.1.1.1 32

[R2]bgp 200
[R2-bgp]peer 12.1.1.1 as-number 100
[R2-bgp]peer 21.1.1.1 as-number 100

2）查看BGP路由表

[R2]display bgp routing-table 1.1.1.1

 BGP local router ID : 2.2.2.2
 Local AS number : 200
 Paths:   2 available, 1 best, 1 select
 BGP routing table entry information of 1.1.1.1/32:
 From: 12.1.1.1 (1.1.1.1)
 Route Duration: 00h00m30s  
 Direct Out-interface: GigabitEthernet0/0/1
 Original nexthop: 12.1.1.1
 Qos information : 0x0
 AS-path 100, origin igp, MED 0, pref-val 0, valid, external, best, select, active, pre 255
 Advertised to such 2 peers:
    12.1.1.1
    21.1.1.1
 BGP routing table entry information of 1.1.1.1/32:
 From: 21.1.1.1 (1.1.1.1)
 Route Duration: 00h00m29s  
 Direct Out-interface: GigabitEthernet0/0/0
 Original nexthop: 21.1.1.1
 Qos information : 0x0
 AS-path 100, origin igp, MED 0, pref-val 0, valid, external, pre 255, not preferred for peer address
 Not advertised to any peer yet

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