BGp
实验：了解BGP的概念和配置
实验拓扑：
实验步骤：
先配置各个接口：
配置基本的BGP网络，
在R1上：
router bgp 1
bgp router-id 1.1.1.1
neighbor 12.12.12.2 remote-as 5
no synchronization
在R2上：
router bgp 5
bgp router-id 2.2.2.2
neighbor 12.12.12.1 remote-as 1
no synchronization
你可以用show ip bgp neighbors 查看它现在的邻居关系。
接下来，如果我们想要R1与R3建立ＩＢＧＰ关系，那么我们需要在R1，R2，R3之间公布ＯＳＰＦ路由，
R2(config)#router ospf 100
R2(config-router)#net 12.12.12.0 0.0.0.255 area 0
R2(config-router)#net 2.2.2.0 0.0.0.255 area 0
R5(config)#router ospf 100
R5(config-router)#net 25.25.25.0 0.0.0.255 area 0
R5(config-router)#net 35.35.35.0 0.0.0.255 area 0
R5(config-router)#net 5.5.5.0 0.0.0.255 area 0
R3(config)#router ospf 100
R3(config-router)#net 3.3.3.0 0.0.0.255 area 0
R3(config-router)#net 35.35.35.0 0.0.0.255 area 0
好的，现在我们在Ｒ１上配置，让它与Ｒ３和R2形成ＩＢＧＰ关系。那么我们在这里需要配置：
R2：
R2(config)router bgp 5
R2(config-router)#neighbor 3.3.3.3 remote-as 5
R2(config-router)#neighbor 3.3.3.3 next-hop-self
R2(config-router)#neighbor 3.3.3.3 update-source lo1
R2(config-router)#neighbor 5.5.5.5 remote-as 5
R2(config-router)#neighbor 5.5.5.5 next-hop-self
R2(config-router)#neighbor 5.5.5.5 update-source lo1
R5：
R5(config)#router bgp 5
R5(config-router)#no synchronization
R5(config-router)#bgp router-id 5.5.5.5
R5(config-router)#neighbor huo peer-group
R5(config-router)#neighbor huo remote-as 5
R5(config-router)#neighbor huo update-source lo1
R5(config-router)#neighbor 2.2.2.2 peer-group huo
R5(config-router)#neighbor 3.3.3.3 peer-group huo
R3：
R3(config)#router bgp 5
R3(config-router)#bgp router-id 3.3.3.3
R3(config-router)#no synchronization
R3(config-router)#neighbor 2.2.2.2 remote-as 5
R3(config-router)#neighbor 2.2.2.2 next-hop-self
R3(config-router)#neighbor 2.2.2.2 update-source lo1
R3(config-router)#neighbor 5.5.5.5 remote-as 5
R3(config-router)#neighbor 5.5.5.5 next-hop-s
R3(config-router)#neighbor 5.5.5.5 update-source lo1
好的，现在R1、R2、R3的邻居关系就起来了。
接下来我们需要来配置R3与R5的邻居关系：
R4
R4(config)#router bgp 4
R4(config-router)#bgp router-id 4.4.4.4
R4(config-router)#no synchronization
R4(config-router)#neighbor 34.34.34.3 remote-as 5
R3
R3(config-router)#neighbor 34.34.34.4 remote-as 4
然后在R1和R4上来公布网段：
R1：
router bgp 1
network 1.1.1.0 mask 255.255.255.0
R4：
router bgp 4
network 4.4.4.0 mask 255.255.255.0
在这里，我们必须看到BGP的neighbor关系UP起来才行：
在路由器上show ip bgp
如果看到的条目没有“>”，则表明该条目不优化，它不会放进路由表，也不传给BGP邻居。那么我们需要做两件事：
1. No synchronization 关闭自动同步
2.指定下一跳，我们一般用的是 next-hop-self
如果在Ebgp网络中用回环口建邻居，那么我们需要配置：
Router bgp x
Bgp router-id
Neighbor x.x.x.x remote-as 1
Neighbor x.x.x.x ebgp-multihop 2
Ip route x.x.x.x 255.255.255.255 接口
我们用扩展ping来PING4.4.4.4
这样，BGp的实验就成功了：
我们把配置全部粘贴出来
R1：
R1#show run
interface Loopback1
ip address 1.1.1.1 255.255.255.0
!
interface Serial0
ip address 12.12.12.1 255.255.255.0
!
router bgp 1
no synchronization
bgp router-id 1.1.1.1
bgp log-neighbor-changes
network 1.1.1.0 mask 255.255.255.0
neighbor 12.12.12.2 remote-as 5
R2：
R2#show run
!
interface Loopback1
ip address 2.2.2.2 255.255.255.0
!
interface Serial0
ip address 12.12.12.2 255.255.255.0
clockrate 64000
!
interface Serial1
ip address 25.25.25.2 255.255.255.0
!
router ospf 100
log-adjacency-changes
network 2.2.2.0 0.0.0.255 area 0
network 25.25.25.0 0.0.0.255 area 0
!
router bgp 5
no synchronization
bgp router-id 2.2.2.2
bgp log-neighbor-changes
neighbor 3.3.3.3 remote-as 5
neighbor 3.3.3.3 update-source Loopback1
neighbor 3.3.3.3 next-hop-self
neighbor 5.5.5.5 remote-as 5
neighbor 5.5.5.5 update-source Loopback1
neighbor 5.5.5.5 next-hop-self
neighbor 12.12.12.1 remote-as 1
!
R5：
R5#show run
hostname R5
!
interface Loopback1
ip address 5.5.5.5 255.255.255.0
!
interface Serial1
ip address 25.25.25.5 255.255.255.0
clockrate 64000
!
interface Serial4
ip address 35.35.35.5 255.255.255.0
clockrate 64000
!
router ospf 100
log-adjacency-changes
network 5.5.5.0 0.0.0.255 area 0
network 25.25.25.0 0.0.0.255 area 0
network 35.35.35.0 0.0.0.255 area 0
!
router bgp 5
no synchronization
bgp router-id 5.5.5.5
bgp log-neighbor-changes
neighbor huo peer-group
neighbor huo remote-as 5
neighbor huo update-source Loopback1
neighbor 2.2.2.2 peer-group huo
neighbor 3.3.3.3 peer-group huo
R3
R3#show run
!
hostname R3
!
interface Loopback1
ip address 3.3.3.3 255.255.255.0
!
interface Serial0
ip address 34.34.34.3 255.255.255.0
clockrate 64000
!
interface Serial1
ip address 35.35.35.3 255.255.255.0
!
router ospf 100
log-adjacency-changes
network 3.3.3.0 0.0.0.255 area 0
network 35.35.35.0 0.0.0.255 area 0
!
router bgp 5
no synchronization
bgp router-id 3.3.3.3
bgp log-neighbor-changes
neighbor 2.2.2.2 remote-as 5
neighbor 2.2.2.2 update-source Loopback1
neighbor 2.2.2.2 next-hop-self
neighbor 5.5.5.5 remote-as 5
neighbor 5.5.5.5 update-source Loopback1
neighbor 5.5.5.5 next-hop-self
neighbor 34.34.34.4 remote-as 4
!
R4#show run
hostname R4
!
interface Loopback1
ip address 4.4.4.4 255.255.255.0
!
interface Serial0
ip address 34.34.34.4 255.255.255.0
!
router bgp 4
no synchronization
bgp router-id 4.4.4.4
bgp log-neighbor-changes
network 4.4.4.0 mask 255.255.255.0
neighbor 34.34.34.3 remote-as 5