BGP之过滤，汇聚

要求：

1.在R2上过滤22.2.2.0/24 23.3.16.0/20这两个网段

2.比较route-map，distribute-list， ip prefix-list过滤的区别

interface Loopback0

ip address 1.1.1.1 255.255.255.0

interface Loopback1

ip address 21.0.0.1 255.255.255.0

interface Loopback2

ip address 22.2.2.1 255.255.255.0

interface Loopback3

ip address 23.3.0.1 255.255.240.0

interface Loopback4

ip address 23.3.16.1 255.255.240.0

interface Loopback5

ip address 23.3.32.1 255.255.224.0

interface Loopback6

ip address 23.3.64.1 255.255.192.0

interface Loopback7

ip address 23.3.128.1 255.255.128.0

interface Ethernet0/0

ip address 12.1.1.1 255.255.255.0

half-duplex

router bgp 123

no synchronization

bgp router-id 1.1.1.1

bgp log-neighbor-changes

network 21.0.0.0 mask 255.255.255.0

network 22.2.2.0 mask 255.255.255.0

network 23.3.0.0 mask 255.255.240.0

network 23.3.16.0 mask 255.255.240.0

network 23.3.32.0 mask 255.255.224.0

network 23.3.64.0 mask 255.255.192.0

network 23.3.128.0 mask 255.255.128.0

neighbor 12.1.1.2 remote-as 110

no auto-summary

ip address 2.2.2.2 255.255.255.255

ip address 12.1.1.2 255.255.255.0

interface Ethernet0/1

ip address 23.1.1.2 255.255.255.0

interface Ethernet0/2

ip address 24.1.1.2 255.255.255.0

interface Ethernet0/3

ip address 25.1.1.2 255.255.255.0

router ospf 10

router-id 2.2.2.2

log-adjacency-changes

network 2.2.2.2 0.0.0.0 area 0

network 12.1.1.0 0.0.0.255 area 0

network 23.1.1.0 0.0.0.255 area 0

network 24.1.1.0 0.0.0.255 area 0

network 25.1.1.0 0.0.0.255 area 0

router bgp 110

neighbor 3.3.3.3 remote-as 110

neighbor 3.3.3.3 update-source Loopback0

neighbor 3.3.3.3 distribute-list liang out

neighbor 4.4.4.4 remote-as 110

neighbor 4.4.4.4 update-source Loopback0

neighbor 4.4.4.4 route-map liang out

neighbor 5.5.5.5 remote-as 110

neighbor 5.5.5.5 update-source Loopback0

neighbor 5.5.5.5 prefix-list liang out

neighbor 12.1.1.1 remote-as 123

ip prefix-list liang seq 5 deny 22.2.2.0/24

ip prefix-list liang seq 10 deny 23.3.16.0/20

ip prefix-list liang seq 15 permit 0.0.0.0/0 le 32

ip access-list extended liang

deny ip host 22.2.2.0 host 255.255.255.0

deny ip host 23.3.16.0 host 255.255.240.0

permit ip any any

route-map liang permit 10

match ip address liang

control-plane

R3#show ip bgp

BGP table version is 24, local router ID is 3.3.3.3

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

*>i21.0.0.0/24 12.1.1.1 0 100 0 123 i

*>i23.3.0.0/20 12.1.1.1 0 100 0 123 i

*>i23.3.32.0/19 12.1.1.1 0 100 0 123 i

*>i23.3.64.0/18 12.1.1.1 0 100 0 123 i

*>i23.3.128.0/17 12.1.1.1 0 100 0 123 i

R4#show ip bgp

BGP table version is 24, local router ID is 4.4.4.4

R5#show ip bgp

BGP table version is 34, local router ID is 5.5.5.5

总结：

1.route-map对于多条过滤条目，并没有任何优势比起ip prefix-list，distribute，ACL

2.推荐选用prefix过滤路由条目，因为prefix可以匹配mask长度

3.过于路径的过滤可以选用filter-list 及其正则表达式

4.对于过滤路由条目，R2上不能配置peer-group

1. advertise-map Set condition to advertise attribute

as-set Generate AS set path information

attribute-map Set attributes of aggregate

nlri Nlri aggregate applies to

route-map Set parameters of aggregate

summary-only Filter more specific routes from updates

suppress-map Conditionally filter more specific routes from update 区别及其用途

2.AS2有个10.1.3.0/24 AS3有个10.1.1.0/24，AS4有个10.1.2.0/24

步骤：

在R2上做汇聚

不做汇聚情况

R1#show ip bgp

BGP table version is 1, local router ID is 1.1.1.1

* i10.1.1.0/24 24.1.1.4 0 100 0 3 i

* i10.1.2.0/24 26.1.1.6 0 100 0 4 i

* i10.1.3.0/24 23.1.1.3 0 100 0 2 i

BGP table version is 4, local router ID is 1.1.1.1

*>i10.1.1.0/24 2.2.2.2 0 100 0 3 i

*>i10.1.2.0/24 2.2.2.2 0 100 0 4 i

*>i10.1.3.0/24 2.2.2.2 0 100 0 2 i

R2(config-router)#aggregate-address 10.1.1.0 255.255.252.0

BGP table version is 5, local router ID is 1.1.1.1

*>i10.1.0.0/22 2.2.2.2 0 100 0 i

R2#show ip bgp

BGP table version is 5, local router ID is 2.2.2.2

*> 10.1.0.0/22 0.0.0.0 32768 i

*> 10.1.1.0/24 24.1.1.4 0 3 i

*> 10.1.2.0/24 26.1.1.6 0 0 4 i

*> 10.1.3.0/24 23.1.1.3 0 0 2 i

默认的情况下明细聚合路由都传递，而聚合路由是0.0.0.0本地起源的。

默认的是原子聚合所谓的原子聚合就是说明路由已经被汇聚，默认的明细路由的属性消失

R2(config-router)#aggregate-address 10.1.1.0 255.255.252.0 summary-only

BGP table version is 8, local router ID is 1.1.1.1

BGP table version is 8, local router ID is 2.2.2.2

s> 10.1.1.0/24 24.1.1.4 0 3 i

s> 10.1.2.0/24 26.1.1.6 0 0 4 i

s> 10.1.3.0/24 23.1.1.3 0 0 2 i

打上summary-only只传递聚合路由，在聚合者路由上明细路由被抑制

这时我们说下suppress-map，我们想让10.1.1.0/24路由不被抑制R2配置如下

access-list 100 permit ip host 10.1.1.0 host 255.255.255.0

route-map liang deny 10

match ip address 100

route-map liang permit 20

R2(config-router)#$1.1.0 255.255.252.0 summary-only suppress-map liang

BGP table version is 15, local router ID is 2.2.2.2

BGP table version is 15, local router ID is 1.1.1.1

假如我们把10.1.1.0/24抑制掉

Access-list 101 permit ip host 10.1.1.0 mask 255.255.255.0

route-map liang premit 10

Match ip add 101

记着在这不能再打 route-map liang permit 20如果这样就是允许了就不能把这个条目抑制掉了

as-set

R2(config-router)#$ddress 10.1.1.0 255.255.252.0 summary-only as-set

BGP table version is 22, local router ID is 1.1.1.1

*>i10.1.0.0/22 2.2.2.2 0 100 0 {3,4,2} i

还原原来的明细路由属性

attribute-map/route-map 定义控制聚合的属性只对聚合后的路由起作用

Extended IP access list 100

10 permit ip host 10.1.1.0 host 255.255.255.0 (1 match)

R2(config)#route-map test permit 10

R2(config-route-map)#ma

R2(config-route-map)#match ip add 101

R2(config-route-map)#set ?

as-path Prepend string for a BGP AS-path attribute

automatic-tag Automatically compute TAG value

comm-list set BGP community list (for deletion)

community BGP community attribute

dampening Set BGP route flap dampening parameters

default Set default information

extcommunity BGP extended community attribute

interface Output interface

ip IP specific information

ipv6 IPv6 specific information

level Where to import route

local-preference BGP local preference path attribute

metric Metric value for destination routing protocol

metric-type Type of metric for destination routing protocol

mpls-label Set MPLS label for prefix

nlri BGP NLRI type

origin BGP origin code

tag Tag value for destination routing protocol

traffic-index BGP traffic classification number for accounting

vrf Define VRF name

weight BGP weight for routing table

设置聚合后的属性值

Advertise-map----只对advertise-map里面匹配的路由进行聚合。当advertise-map里面匹配的明细路由全部消失后，即使聚合路由范围内还有其他明细路由，聚合路由也将消失。当与as－set合用时，只继承advertise-map里面匹配的明细路由的属性。

定义宣告没有进来之前那些明细路由应该被聚合

As-set----让聚合路由继承明细路由的属性，包括：as-path，local_preference，community，origin－code。与advertise-map合用，只继承advertise-map里面匹配的明细路由的属性。

默认是产生的汇聚路由是本地始发的也就是下一跳0.0.0.0的路由，他会抑制掉汇聚之前AS路径的信息

打上AS-SET 会继承明细路由的属性

Attribute－map和route－map----这两个参数一样，可以将聚合路由的属性清除掉（除了as-path属性），添加自己需要添加的属性。

只影响聚合后的路由的属性也就是给聚合路由加属性不加as-set 默认是原子聚合

Summary-only----将聚合路由所包括的所有明细路由都抑制掉，被抑制的路由在bgp的转发表里，显示为s，代表suppress的意思。发送更新时，只发送聚合路由。可以与neighbor 1.1.1.1 unsuppress-map XX合用，对特定邻居漏过特定的明细路由。

Suppress－map----将suppress－map里面匹配的路由抑制掉，被抑制的路由在bgp的转发表里，显示为s，代表suppress的意思。发送更新时，只发送聚合路由和没有被抑制的明细路由。可以neighbor 1.1.1.1 unsuppress-map XX合用，对特定邻居漏过特定的明细路由。

permit为抑制不转发 deny为不抑制也就是转发

本文转自q狼的诱惑 51CTO博客，原文链接：http://blog.51cto.com/liangrui/572745，如需转载请自行联系原作者

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