当一台路由器，收到一个bgp的路由带有no-export属性是这台路由器就不会再向EBGP对等体及IBGP对等体发送该路由了
拓扑：

R3#sh ip bgp
BGP table version is 1, local router ID is 10.2.2.2
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
* i172.16.1.0/24 10.1.1.1 0 100 0 1 i
* i172.16.2.0/24 10.1.1.1 0 100 0 1 i
* i172.16.3.0/24 10.1.1.1 0 100 0 1 i

不是最优的，在R2做NEXT-HOP-SELF
R2(config)#router bgp 2
R2(config-router)#nei 10.2.2.2 next-hop-self

再查看R3的路由表
R3#sh ip bgp
BGP table version is 4, local router ID is 10.2.2.2
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
*>i172.16.1.0/24 10.2.2.1 0 100 0 1 i
*>i172.16.2.0/24 10.2.2.1 0 100 0 1 i
*>i172.16.3.0/24 10.2.2.1 0 100 0 1 i

做no-advertise
R1(config)#access-list 1 per 172.16.3.0 0.0.0.255
R1(config)#route-map ccxx per 10
R1(config-route-map)#ma ip add 1
R1(config-route-map)#set community no-advertise
R1(config-route-map)#exi
R1(config)#route-map ccxx per 20
R1(config-route-map)#exi
R1(config)#router bgp 1
R1(config-router)#nei 10.1.1.2 route-map ccxx out
R1(config-router)#nei 10.1.1.2 send-community

查看R3的路由表：
R3#sh ip bgp
BGP table version is 5, local router ID is 10.2.2.2
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
*>i172.16.1.0/24 10.2.2.1 0 100 0 1 i
*>i172.16.2.0/24 10.2.2.1 0 100 0 1 i

没学到172.16.3.0网段。再验证下是不是用了NO-ADVERTISE
R2#sh ip bgp 172.16.3.1
BGP routing table entry for 172.16.3.0/24, version 5
Paths: (1 available, best #1, table Default-IP-Routing-Table, not advertised to any peer)
Not advertised to any peer
1
10.1.1.1 from 10.1.1.1 (172.16.1.1)
Origin IGP, metric 0, localpref 100, valid, external, best
Community: no-advertise