BGP的基础知识以及特性讲解(7)

汇总在什么AS 配置，就自动携带该AS 的AS 号，作为其路径信息，而默认不携带明细子网的AS 信息。 2:EBGP汇总

R2#sh ip bgp 1.0.0.0

BGP routing table entry for 1.0.0.0/8, version 8

Paths: (1 available, best #1, table Default-IP-Routing-Table) Advertised to non peer-group peers: 12.12.12.1 23.23.23.2

1, (aggregated by 2 23.23.23.1)

0.0.0.0 from 0.0.0.0 (23.23.23.1)

Origin IGP, localpref 100, weight 32768, valid, aggregated, local, best

如上显示信息中不会再有AUTOMIC_AGGREAGATE 属性，因为使用了AS-SET 参数，所以不 会发生AS 信息的丢失，所以不需要该属性进行警告。

2.1 R1 1.0.0.0/8----R2----R3! R3--1.0.0.0/8----R1 ,R1 学还是不学

2.2 R2 做1.0.0.0/8---R3 ！Ｒ３－－－Ｒ１，Ｒ１ 学还是不学。

汇总是发生在本地，还是发生在对等体

3：汇总子参数选项

3.1 summary-only

指定只有汇总路由可以当做BGP 更新发送给PEER,而明细路由，全部被抑制。

Aggregate-address 1.0.0.0 255.0.0.0 summary-only R1#sh ip bgp

BGP table version is 4, local router ID is 1.1.1.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path *> 1.0.0.0 0.0.0.0 32768 i s> 1.1.1.0/24 0.0.0.0 0 32768 i R1#sh ip bgp 1.1.1.0 255.255.255.0

BGP routing table entry for 1.1.1.0/24, version 4

Paths: (1 available, best #1, table Default-IP-Routing-Table, Advertisements suppressed by an aggregate.) Not advertised to any peer Local

0.0.0.0 from 0.0.0.0 (1.1.1.1)

Origin IGP, metric 0, localpref 100, weight 32768, valid, sourced, local, best R1#

3.2 suppress-map

该子选项作用是指定具体的明细路由被抑制，而其他未被抑制的明细路由会伴随汇总路由一起发送给 PEER。 access-list 1 permit 1.1.1.0 !

route-map SUP permit 10 match ip address 1 !

aggregate-address 1.0.0.0 255.0.0.0 suppress-map SUP

如果ROUTE-MAP 被抑制映射，属性映射所套用，是不需要写空条目的，此时没路由过滤功能。 R1#sh ip bgp

BGP table version is 5, local router ID is 1.2.2.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path *> 1.0.0.0 0.0.0.0 32768 i s> 1.1.1.0/24 0.0.0.0 0 32768 i *> 1.2.2.0/24 0.0.0.0 0 32768 i

3.3 attribute-map

属性映射可以将起源代码进行相应修改。 I ? E

access-list 1 per 1.0.0.0 255.0.0.0 route-map SA permit 10 match ip address 1 set origin incomplete

aggregate-address 1.0.0.0 255.0.0.0 attribute-map SA

3.4 advertise-map

公告用于指定汇总路由继承特定明细路由的路由属性。

在R4 上对172.16.3.0 路由进行团体属性的设置 access-list 1 permit 172.16.3.0 0.0.0.255 !

route-map SC permit 10 match ip address 1

set community no-export

neighbor 24.24.24.1 route-map SC out neighbor 24.24.24.1 send-community

R2#show ip bgp 172.16.3.0

BGP routing table entry for 172.16.3.0/24, version 4

Paths: (1 available, best #1, table Default-IP-Routing-Table) Advertised to non peer-group peers: 12.12.12.1 23.23.23.2 4

24.24.24.2 from 24.24.24.2 (172.16.3.1)

Origin IGP, metric 0, localpref 100, valid, external, best

R2#sh ip bgp community no-export

BGP table version is 5, local router ID is 24.24.24.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path *> 172.16.3.0/24 24.24.24.2 0 0 4 i R2#

R2#sh ip bgp

BGP table version is 9, local router ID is 24.24.24.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path *> 172.16.0.0 0.0.0.0 100 32768 {1,4} i

s> 172.16.1.0/24 12.12.12.1 0 0 1 i

s> 172.16.2.0/24 12.12.12.1 0 0 1 i s> 172.16.3.0/24 24.24.24.2 0 0 4 i

R2#sh ip bgp community no-export

BGP table version is 9, local router ID is 24.24.24.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path *> 172.16.0.0 0.0.0.0 100 32768 {1,4} i

s> 172.16.3.0/24 24.24.24.2 0 0 4 i

access-list 1 permit 172.16.1.0 access-list 1 permit 172.16.2.0

这里编写Acl 匹配172.16.1.0 172.16.2.0 的目的是让公告映射去继承被匹配到的明细子网属性

自然172.16.3.0 是不被匹配，那么公告映射就不会让汇总路由继承172.16.3.0 的NO-EXPORT 属性，自然汇总路由就会发送EBGP PEER。 !

route-map SA permit 10 match ip address 1 ！

aggregate-address 172.16.0.0 255.255.0.0 as-set summary-only advertise-map SA

R2#sh ip bgp community

BGP table version is 10, local router ID is 24.24.24.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path s> 172.16.3.0/24 24.24.24.2 0 0 4 i

3.5 AS-SET

AS-SET 保留AS 号，防止AS 信息丢失

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