1.优选规则
1)优选Preferred_Value属性最大的路由。(华为私有属性,只在本地有效)
2)优选Local_Preferred属性最大的路由。
3)本地始发的BGP路由优于从其他对等体学习的路由。
4)优选AS_Path属性值最短的路由。
5)优选Origin属性值最短的路由。
6)优选MED属性值最小的路由。
7)优选从EBGP对等体学来的路由(EBGP路由优先级高于IBGP路由)。
8)优选Next_Hop的IGP度量值最小的路由。
9)优选Cluster_List最短的路由。
10)优选Router-ID最小的设备通过的路由。
11)优选具有最小IP地址的对等体通告的路由。
2.优选Preferred_Value属性最大的路由
1)基本配置
[R1]bgp 100
[R1-bgp]router-id 1.1.1.1
[R1-bgp]peer 12.1.1.2 as-number 200
[R1-bgp]peer 13.1.1.3 as-number 300
[R1-bgp]network 1.1.1.1 32
[R2]bgp 200
[R2-bgp]router-id 2.2.2.2
[R2-bgp]peer 12.1.1.1 as-number 100
[R2-bgp]peer 24.1.1.4 as-number 400
[R3]bgp 300
[R3-bgp]router-id 3.3.3.3
[R3-bgp]peer 13.1.1.1 as-number 100
[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 200
[R4-bgp]peer 34.1.1.3 as-number 300
2)查看BGP路由表
[R4]display bgp routing-table
Network NextHop MED LocPrf PrefVal Path/Ogn
*> 1.1.1.1/32 24.1.1.2 0 200 100i
* 34.1.1.3 0 300 100i
[R4-bgp]display bgp routing-table 1.1.1.1
AS-path 200 100, origin igp, pref-val 0, valid, external, best, select, active, pre 255
AS-path 300 100, origin igp, pref-val 0, valid, external, pre 255, not preferred for router ID
3)修改Preferred_Value属性
[R4-bgp]peer 34.1.1.3 preferred-value 6000
[R4]display bgp routing-table
Network NextHop MED LocPrf PrefVal Path/Ogn
*> 1.1.1.1/32 34.1.1.3 6000 300 100i
* 24.1.1.2 0 200 100i
[R4-bgp]display bgp routing-table 1.1.1.1
Original nexthop: 34.1.1.3
AS-path 300 100, origin igp, pref-val 6000, valid, external, best, select, active, pre 255
Original nexthop: 24.1.1.2
AS-path 200 100, origin igp, pref-val 0, valid, external, pre 255, not preferred for PreVal
3.优选Local_Preferred属性最大的路由
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 34.1.1.0 0.255.255.255
[R3-ospf-1-area-0.0.0.0]network 3.3.3.3 0.0.0.0
[R4]ospf 1 router-id 4.4.4.4
[R4-ospf-1]area 0
[R4-ospf-1-area-0.0.0.0]network 24.1.1.0 0.255.255.255
[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 4.4.4.4 0.0.0.0
2)配置BGP
[R1]bgp 100
[R1-bgp]router-id 1.1.1.1
[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]router-id 2.2.2.2
[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]router-id 3.3.3.3
[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]router-id 4.4.4.4
[R4-bgp]peer 2.2.2.2 as-number 234
[R4-bgp]peer 2.2.2.2 connect-interface LoopBack 0
[R4-bgp]peer 2.2.2.2 reflect-client
[R4-bgp]peer 3.3.3.3 as-number 234
[R4-bgp]peer 3.3.3.3 connect-interface LoopBack 0
[R4-bgp]peer 3.3.3.3 reflect-client
2)查看BGP路由表
[R4]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
3)修改Local_Preferred属性
[R3]ip ip-prefix 1 permit 1.1.1.1 32
[R3]route-policy dsrw.com permit node 10
[R3-route-policy]if-match ip-prefix 1
[R3-route-policy]apply local-preference 200
[R3]bgp 234
[R3-bgp]peer 4.4.4.4 route-policy dsrw.com export
4)查看BGP路由表
<R4>display bgp routing-table
Network NextHop MED LocPrf PrefVal Path/Ogn
*>i 1.1.1.1/32 3.3.3.3 0 200 0 100i
4.本地始发的BGP路由优于从其他对等体学习的路由
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
[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)R1、R3引入1.1.1.1/32,查看BGP路由(NextHop 为0.0.0.0路由被选中)
[R1-bgp]network 1.1.1.1 32
[R3-bgp]network 1.1.1.1 32
[R1-bgp]display bgp routing-table
Network NextHop MED LocPrf PrefVal Path/Ogn
*> 1.1.1.1/32 0.0.0.0 0 0 i
* i 3.3.3.3 1 100 0 i
[R3-bgp]display bgp routing-table
Network NextHop MED LocPrf PrefVal Path/Ogn
*> 1.1.1.1/32 0.0.0.0 1 0 i
i 1.1.1.1 0 100 0 i
优选AS_Path属性值最短的路由
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
[R1-bgp]display bgp routing-table
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
3)修改AS_Path属性后查看BGP路由表
[R1-route-policy]display bgp routing-table
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
[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 as-path 200 200 additive
[R2]bgp 200
[R2-bgp]peer 12.1.1.1 route-policy dsrw.com export
[R1-route-policy]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: 00h13m07s
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: 00h02m38s
Direct Out-interface: GigabitEthernet0/0/0
Original nexthop: 12.1.1.2
Qos information : 0x0
AS-path 200 200 200, origin igp, MED 0, pref-val 0, valid, external, pre 255, not preferred for AS-Path
Not advertised to any peer yet
[R1-route-policy]display bgp routing-table
Network NextHop MED LocPrf PrefVal Path/Ogn
*>i 2.2.2.2/32 3.3.3.3 0 100 0 200i
* 12.1.1.2 0 0 200 200 200i
6.优选Origin属性值最短的路由
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
[R1-bgp]display bgp routing-table
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
3)修改Origin属性后查看BGP路由表
[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 origin incomplete
[R2]bgp 200
[R2-bgp]peer 12.1.1.1 route-policy dsrw.com export
<R1>display bgp routing-table
Network NextHop MED LocPrf PrefVal Path/Ogn
*>i 2.2.2.2/32 3.3.3.3 0 100 0 200i
* 12.1.1.2 0 0 200?
<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: 00h41m38s
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: 00h00m55s
Direct Out-interface: GigabitEthernet0/0/0
Original nexthop: 12.1.1.2
Qos information : 0x0
AS-path 200, origin incomplete, MED 0, pref-val 0, valid, external, pre 255, not preferred for Origin
Not advertised to any peer yet
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