＜Community＞主要用來控制路由的傳播範圍
社團屬性，也叫共同體屬性，是可選傳遞屬性
·“可選”：意味着並不是所有的路由器都能識別這個社團屬性。
·“傳遞”：意味着路由器即使不能識別這個屬性，也能將這條路由繼續傳遞下去。
·社團屬性類似於tag標記，它允許路由器能夠使用一個指示符來標記路由，並且允許其它路由器根據這個標記來控制路由的傳播範圍,或者對含有標記的路由做一些處理。一條路由可以設置多個社團屬性，也就是說允許同時打上多個標記
要去：
1.證明團體屬性的區別及其傳播範圍
2.聯盟的應用
3.反射器的應用
R1配置
interface Loopback0
ip address 1.1.1.1 255.255.255.0
interface Loopback1
ip address 1.1.2.1 255.255.255.0
interface Loopback2
ip address 1.1.3.1 255.255.255.0
interface Loopback3
ip address 1.1.4.1 255.255.255.0
interface Serial0/0
ip address 12.1.1.1 255.255.255.0
serial restart-delay 0
router ospf 10
router-id 1.1.1.1
log-adjacency-changes
network 1.1.1.0 0.0.0.255 area 0
network 1.1.2.0 0.0.0.255 area 0
network 1.1.3.0 0.0.0.255 area 0
network 1.1.4.0 0.0.0.255 area 0
network 12.1.1.0 0.0.0.255 area 0
!router bgp 65535
no synchronization
bgp router-id 1.1.1.1
bgp log-neighbor-changes
bgp confederation identifier 1
network 1.1.1.0 mask 255.255.255.0
network 1.1.2.0 mask 255.255.255.0
network 1.1.3.0 mask 255.255.255.0
network 1.1.4.0 mask 255.255.255.0
neighbor 2.2.2.2 remote-as 65535
neighbor 2.2.2.2 update-source Loopback0
neighbor 2.2.2.2 next-hop-self
neighbor 2.2.2.2 send-community
neighbor 2.2.2.2 route-map liang out
no auto-summary
ip bgp-community new-format
access-list 10 permit 1.1.1.0
access-list 20 permit 1.1.2.0
access-list 30 permit 1.1.3.0
access-list 40 permit 1.1.4.0
route-map liang permit 10
match ip address 10
set community no-advertise
route-map liang permit 20
match ip address 20
set community no-export
route-map liang permit 30
match ip address 30
set community local-AS
route-map liang permit 40
match ip address 40
set community internet
R2的配置
interface Loopback0
ip address 2.2.2.2 255.255.255.0
interface Serial0/0
ip address 12.1.1.2 255.255.255.0
serial restart-delay 0
interface Serial0/1
ip address 23.1.1.2 255.255.255.0
serial restart-delay 0
interface Serial0/2
ip address 24.1.1.2 255.255.255.0
serial restart-delay 0
router ospf 10
router-id 2.2.2.2
log-adjacency-changes
network 2.2.2.0 0.0.0.255 area 0
network 12.1.1.0 0.0.0.255 area 0
network 23.1.1.0 0.0.0.255 area 0
router bgp 65535
no synchronization
bgp router-id 2.2.2.2
bgp log-neighbor-changes
bgp confederation identifier 1
bgp confederation peers 65534
neighbor 1.1.1.1 remote-as 65535
neighbor 1.1.1.1 update-source Loopback0
neighbor 3.3.3.3 remote-as 65535
neighbor 3.3.3.3 update-source Loopback0
neighbor 3.3.3.3 route-reflector-client
neighbor 3.3.3.3 next-hop-self
neighbor 3.3.3.3 send-community
neighbor 4.4.4.4 remote-as 65534
neighbor 4.4.4.4 send-community
neighbor 24.1.1.4 remote-as 65534
neighbor 24.1.1.4 ebgp-multihop 255
neighbor 24.1.1.4 next-hop-self
neighbor 24.1.1.4 send-community
no auto-summary
ip bgp-community new-format
R3的配置
interface Loopback0
ip address 3.3.3.3 255.255.255.0
interface Serial0/1
ip address 23.1.1.3 255.255.255.0
serial restart-delay 0
router ospf 10
router-id 3.3.3.3
log-adjacency-changes
network 3.3.3.0 0.0.0.255 area 0
network 23.1.1.0 0.0.0.255 area 0
router bgp 65535
no synchronization
bgp router-id 3.3.3.3
bgp log-neighbor-changes
bgp confederation identifier 1
neighbor 2.2.2.2 remote-as 65535
neighbor 2.2.2.2 update-source Loopback0
no auto-summary
R4的配置
interface Loopback0
ip address 4.4.4.4 255.255.255.0
interface Serial0/2
ip address 24.1.1.4 255.255.255.0
serial restart-delay 0
interface Serial0/3
ip address 45.1.1.4 255.255.255.0
serial restart-delay 0
router bgp 65534
no synchronization
bgp router-id 4.4.4.4
bgp log-neighbor-changes
bgp confederation identifier 1
bgp confederation peers 65535
neighbor 24.1.1.2 remote-as 65535
neighbor 24.1.1.2 ebgp-multihop 255
neighbor 45.1.1.5 remote-as 2
neighbor 45.1.1.5 ebgp-multihop 255
neighbor 45.1.1.5 send-community
no auto-summary
R5的配置
interface Serial0/3
ip address 45.1.1.5 255.255.255.0
serial restart-delay 0
router bgp 2
no synchronization
bgp router-id 5.5.5.5
bgp log-neighbor-changes
neighbor 45.1.1.4 remote-as 1
no auto-summary
我們是在R1上起四個路由條目並通過route-map抓住打上四個不同的團體屬性值
·社團屬性分以下兩種：
1、well-known communities 公認團體
2、Private communities 私有團體
·社團屬性中已經預定義好的三類well-known屬性:
no-advertise：攜帶此屬性的路由不會通告給任何BGP鄰居。也就是說只傳達給一個鄰居
no-export： 攜帶此屬性的路由不會傳出本AS外,只會傳給IBGP。（聯邦中的小AS會傳遞）。
local-AS： 攜帶此屬性的路由不會傳出小AS。
internat 攜帶此屬性的可以任意傳播不受AS的限制
R2#show ip bgp 四條都有
BGP table version is 7, local router ID is 2.2.2.2
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
*>i1.1.1.0/24 1.1.1.1 0 100 0 i
*>i1.1.2.0/24 1.1.1.1 0 100 0 i
*>i1.1.3.0/24 1.1.1.1 0 100 0 i
*>i1.1.4.0/24 1.1.1.1 0 100 0 i
R3# show ip bgp 因爲1.1.1.0打上的是no-ad的屬性只會傳一跳所以R3上收不到
BGP table version is 8, 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
*>i1.1.2.0/24 1.1.1.1 0 100 0 i
*>i1.1.3.0/24 1.1.1.1 0 100 0 i
*>i1.1.4.0/24 1.1.1.1 0 100 0 i
R4#show ip bgp 1.1.3.0 打上的是local屬性不會傳出小AS(聯盟)所以R4屬於另一個聯盟收不到
BGP table version is 15, local router ID is 4.4.4.4
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
*> 1.1.2.0/24 24.1.1.2 0 100 0 (65535) i
*> 1.1.4.0/24 24.1.1.2 0 100 0 (65535) i
R5# show ip bgp
BGP table version is 25, local router ID is 5.5.5.5
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
*> 1.1.4.0/24 45.1.1.4 0 1 i
在R5上只收到一條internet屬性的條目 no-export 會在大AS內傳播但不會給公有EBGP傳播