如上图所示，R1/R2/R3在同一个IBGP内，这种情况下，路由更新，从IBGP邻居学习的路由不会被传递给其他的IBGP邻居。这样的解决办法有三种：
1、IBGP完全互连
2、路由反射器 （Route Reflector）
3、联盟
案例一、非直连邻居通过路由反射器（直连邻居省略）
R1配置信息：
interface Loopback10
ip address 10.1.1.1 255.255.255.0
!
interface Loopback100
ip address 100.1.1.1 255.255.255.0
!
interface FastEthernet0/0
ip address 1.1.1.1 255.255.255.0
duplex auto
speed auto
！
router bgp 100
no synchronization
bgp log-neighbor-changes
network 10.1.1.0 mask 255.255.255.0
network 100.1.1.0 mask 255.255.255.0
neighbor 20.1.1.1 remote-as 100
neighbor 20.1.1.1 update-source loopback 10
no auto-summary
!
ip route 20.1.1.0 255.255.255.0 1.1.1.2
R2配置信息：
interface Loopback20
ip address 20.1.1.1 255.255.255.0
!
interface FastEthernet0/0
ip address 1.1.1.2 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 2.2.2.2 255.255.255.0
duplex auto
speed auto
!
router bgp 100
no synchronization
bgp log-neighbor-changes
network 1.1.1.0 mask 255.255.255.0
network 2.2.2.0 mask 255.255.255.0
network 20.1.1.0 mask 255.255.255.0
neighbor 2.2.2.3 remote-as 100
neighbor 2.2.2.3 route-reflector-client
neighbor 10.1.1.1 remote-as 100
neighbor 10.1.1.1 update-source Loopback20
neighbor 10.1.1.1 route-reflector-client
no auto-summary
!
ip classless
ip route 10.1.1.0 255.255.255.0 1.1.1.1
R3配置信息：
interface Loopback30
ip address 30.1.1.1 255.255.255.0
!
interface FastEthernet0/1
ip address 2.2.2.3 255.255.255.0
duplex auto
speed auto
!
router bgp 100
no synchronization
bgp log-neighbor-changes
network 30.1.1.0 mask 255.255.255.0
neighbor 2.2.2.2 remote-as 100
no auto-summary
查看R1的路由信息：
R1#show ip route
*Mar 14 08:16:33.956: %SYS-5-CONFIG_I: Configured from console by console
R1#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, FastEthernet0/0
2.0.0.0/24 is subnetted, 1 subnets
B 2.2.2.0 [200/0] via 20.1.1.1, 02:47:19
100.0.0.0/24 is subnetted, 1 subnets
C 100.1.1.0 is directly connected, Loopback100
20.0.0.0/24 is subnetted, 1 subnets
S 20.1.1.0 [1/0] via 1.1.1.2
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, Loopback10
30.0.0.0/24 is subnetted, 1 subnets
B 30.1.1.0 [200/0] via 2.2.2.3, 02:42:23
R1#show ip bgp
BGP table version is 50, local router ID is 100.1.1.1
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
r>i1.1.1.0/24 20.1.1.1 0 100 0 i
*>i2.2.2.0/24 20.1.1.1 0 100 0 i
*> 10.1.1.0/24 0.0.0.0 0 32768 i
r>i20.1.1.0/24 20.1.1.1 0 100 0 i
*>i30.1.1.0/24 2.2.2.3 0 100 0 i
*> 100.1.1.0/24 0.0.0.0 0 32768 i
R2的路由信息：
R2#show ip bgp
BGP table version is 8, local router ID is 20.1.1.1
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
*> 1.1.1.0/24 0.0.0.0 0 32768 i
*> 2.2.2.0/24 0.0.0.0 0 32768 i
r>i10.1.1.0/24 10.1.1.1 0 100 0 i
*> 20.1.1.0/24 0.0.0.0 0 32768 i
*>i30.1.1.0/24 2.2.2.3 0 100 0 i
*>i100.1.1.0/24 10.1.1.1 0 100 0 i
R2#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, FastEthernet0/0
2.0.0.0/24 is subnetted, 1 subnets
C 2.2.2.0 is directly connected, FastEthernet0/1
100.0.0.0/24 is subnetted, 1 subnets
B 100.1.1.0 [200/0] via 10.1.1.1, 00:01:57
20.0.0.0/24 is subnetted, 1 subnets
C 20.1.1.0 is directly connected, Loopback20
10.0.0.0/24 is subnetted, 1 subnets
S 10.1.1.0 [1/0] via 1.1.1.1
30.0.0.0/24 is subnetted, 1 subnets
B 30.1.1.0 [200/0] via 2.2.2.3, 00:01:50
R2#show ip bgp 100.1.1.0
BGP routing table entry for 100.1.1.0/24, version 6
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Advertised to non peer-group peers:
2.2.2.3 -----表示把100.1.1.0/24的路由发布给IBGP邻居2.2.2.3
Local, (Received from a RR-client)
10.1.1.1 from 10.1.1.1 (100.1.1.1)
Origin IGP, metric 0, localpref 100, valid, internal, best
R3的路由信息：
R3#show ip bgp
BGP table version is 6, local router ID is 30.1.1.1
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
*>i1.1.1.0/24 2.2.2.2 0 100 0 i
r>i2.2.2.0/24 2.2.2.2 0 100 0 i
* i10.1.1.0/24 10.1.1.1 0 100 0 i
*>i20.1.1.0/24 2.2.2.2 0 100 0 i
*> 30.1.1.0/24 0.0.0.0 0 32768 i
* i100.1.1.0/24 10.1.1.1 0 100 0 i
R3#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
B 1.1.1.0 [200/0] via 2.2.2.2, 00:03:03
2.0.0.0/24 is subnetted, 1 subnets
C 2.2.2.0 is directly connected, FastEthernet0/1
20.0.0.0/24 is subnetted, 1 subnets
B 20.1.1.0 [200/0] via 2.2.2.2, 00:03:03
30.0.0.0/24 is subnetted, 1 subnets
C 30.1.1.0 is directly connected, Loopback30
可以看到R3上通告的100.1.1.0/24和10.1.1.0/24 网段路由虽然通过BGP学习成功，但是在路由加载的时候添加路由失败，R3上未学习到next hop。
因为在路由同步的规则当中，需要把IGP的路由必须同步到IBGP，如果不能同步就会造成路由黑洞。因此需要在R2上把静态路由重分布
在R2上配置信息：
router bgp 100
no synchronization
bgp log-neighbor-changes
network 1.1.1.0 mask 255.255.255.0
network 2.2.2.0 mask 255.255.255.0
network 20.1.1.0 mask 255.255.255.0
redistribute static metric 10
neighbor 2.2.2.3 remote-as 100
neighbor 2.2.2.3 route-reflector-client
neighbor 10.1.1.1 remote-as 100
neighbor 10.1.1.1 update-source Loopback20
neighbor 10.1.1.1 route-reflector-client
no auto-summary
R3的路由信息：
R3#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
B 1.1.1.0 [200/0] via 2.2.2.2, 00:12:08
2.0.0.0/24 is subnetted, 1 subnets
C 2.2.2.0 is directly connected, FastEthernet0/1
100.0.0.0/24 is subnetted, 1 subnets
B 100.1.1.0 [200/0] via 10.1.1.1, 00:00:01
20.0.0.0/24 is subnetted, 1 subnets
B 20.1.1.0 [200/0] via 2.2.2.2, 00:12:08
10.0.0.0/24 is subnetted, 1 subnets
B 10.1.1.0 [200/10] via 1.1.1.1, 00:00:11
30.0.0.0/24 is subnetted, 1 subnets
C 30.1.1.0 is directly connected, Loopback30
R3#show ip bgp
BGP table version is 8, local router ID is 30.1.1.1
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
*>i1.1.1.0/24 2.2.2.2 0 100 0 i
r>i2.2.2.0/24 2.2.2.2 0 100 0 i
*>i10.1.1.0/24 1.1.1.1 10 100 0 ?
*>i20.1.1.0/24 2.2.2.2 0 100 0 i
*> 30.1.1.0/24 0.0.0.0 0 32768 i
*>i100.1.1.0/24 10.1.1.1 0 100 0 i
在IGP路由同步到IBGP中之后，IBGP邻居就能够正常通过RR学习到相应的路由信息。
初次了解学习BGP，可能理解或解释的不够准确详细，望各位看官见谅！欢迎一起交流探讨~~~