对等体组是对一组路由器实施策略，而社团属性是对一组路由实施策略。
社团属性分以下两种：
1、well-known communities 公认团体 2、Private communities 私有团体社团属性中已经预定义好的三类well-known属性:
- no-advertise：携带此属性的路由不会通告给任何BGP邻居。也就是说只传达给一个邻居
- no-export：携带此属性的路由不会传出本AS外,只会传给IBGP。（联邦中的小AS会递）。
- local-AS： 携带此属性的路由不会传出小AS。
- internat ：携带此属性的可以任意传播不受AS的限制
拓扑：
配置：
| interface Loopback0 ip address 1.1.1.1 255.255.255.255 ! interface Loopback10 ip address 10.1.1.1 255.255.255.0 ! interface Loopback20 ip address 20.1.1.1 255.255.255.0 ! interface Loopback30 ip address 30.1.1.1 255.255.255.0 ! interface Loopback40 ip address 40.1.1.1 255.255.255.0 ! interface FastEthernet0/0 ip address 12.1.1.1 255.255.255.0 duplex auto speed auto ! router bgp 100 no synchronization bgp router-id 1.1.1.1 bgp log-neighbor-changes network 10.1.1.0 mask 255.255.255.0 network 20.1.1.0 mask 255.255.255.0 network 30.1.1.0 mask 255.255.255.0 network 40.1.1.0 mask 255.255.255.0 neighbor 12.1.1.2 remote-as 200 neighbor 12.1.1.2 send-community neighbor 12.1.1.2 route-map community out no auto-summary ! access-list 10 permit 10.1.1.0 0.0.0.255 access-list 20 permit 20.1.1.0 0.0.0.255 access-list 30 permit 30.1.1.0 0.0.0.255 access-list 40 permit 40.1.1.0 0.0.0.255 ! ! ! route-map community permit 10 match ip address 10 set community internet ! route-map community permit 20 match ip address 20 set community local-AS ! route-map community permit 30 match ip address 30 set community no-advertise ! route-map community permit 40 match ip address 40 set community no-export ! route-map community permit 50 |
| interface Loopback0 ip address 2.2.2.2 255.255.255.255 ! interface FastEthernet0/0 ip address 12.1.1.2 255.255.255.0 duplex auto speed auto ! interface FastEthernet0/1 ip address 23.1.1.2 255.255.255.0 duplex auto speed auto ! router ospf 100 router-id 2.2.2.2 log-adjacency-changes network 2.2.2.2 0.0.0.0 area 0 network 23.1.1.0 0.0.0.255 area 0 ! router bgp 400 no synchronization bgp router-id 2.2.2.2 bgp log-neighbor-changes bgp confederation identifier 200 neighbor 3.3.3.3 remote-as 400 neighbor 3.3.3.3 update-source Loopback0 neighbor 3.3.3.3 next-hop-self neighbor 3.3.3.3 send-community neighbor 12.1.1.1 remote-as 100 no auto-summary |
| interface Loopback0 ip address 3.3.3.3 255.255.255.255 ! interface FastEthernet0/0 ip address 34.1.1.3 255.255.255.0 duplex auto speed auto ! interface FastEthernet0/1 ip address 23.1.1.3 255.255.255.0 duplex auto speed auto ! interface FastEthernet1/0 ip address 35.1.1.3 255.255.255.0 speed 100 full-duplex ! router ospf 100 router-id 3.3.3.3 log-adjacency-changes network 3.3.3.3 0.0.0.0 area 0 network 23.1.1.0 0.0.0.255 area 0 network 34.1.1.0 0.0.0.255 area 0 ! router bgp 400 no synchronization bgp log-neighbor-changes bgp confederation identifier 200 bgp confederation peers 500 neighbor 2.2.2.2 remote-as 400 neighbor 2.2.2.2 update-source Loopback0 neighbor 4.4.4.4 remote-as 500 neighbor 4.4.4.4 ebgp-multihop 255 neighbor 4.4.4.4 update-source Loopback0 neighbor 4.4.4.4 send-community neighbor 35.1.1.5 remote-as 300 neighbor 35.1.1.5 send-community no auto-summary |
| interface Loopback0 ip address 4.4.4.4 255.255.255.255 ! interface FastEthernet0/0 ip address 34.1.1.4 255.255.255.0 duplex auto speed auto ! router ospf 100 router-id 4.4.4.4 log-adjacency-changes network 4.4.4.4 0.0.0.0 area 0 network 34.1.1.0 0.0.0.255 area 0 ! router bgp 500 no synchronization bgp router-id 5.5.5.5 bgp log-neighbor-changes bgp confederation identifier 200 bgp confederation peers 400 neighbor 3.3.3.3 remote-as 400 neighbor 3.3.3.3 ebgp-multihop 255 neighbor 3.3.3.3 update-source Loopback0 no auto-summary |
| interface Loopback0 ip address 5.5.5.5 255.255.255.0 ! interface FastEthernet0/0 ip address 35.1.1.5 255.255.255.0 speed 100 full-duplex ! router bgp 300 no synchronization bgp router-id 5.5.5.5 bgp log-neighbor-changes neighbor 35.1.1.3 remote-as 200 no auto-summary |
分析：
R2能接收到所以的社团属性。
由于30.1.1.0携带了 no-advertise 路由不会通告给任何BGP邻居。也就是说只传达给一个居。
所以R3接收不到。
由于20.1.1.0 携带了local-AS，路由不会传出小AS，所以R4接收不到。
由于40.1.1.0携带了no-export，路由不会传出本AS外,只会传给IBGP。（联邦中的小AS会传递）。所以R5接收不到。