bgp配置
r4:
router bgp 4
bgp route-id 4.4.4.4
no au
no syn
neighbor 24.1.1.2 remote-as 123
r2:
router bgp 123
bgp route-id 2.2.2.2
no au
no syn
neighbor 24.1.1.4 remote-as 4
neighbor 3.3.3.3 remote-as 123
neighbor 3.3.3.3 updata-souce lo0
r3:
router bgp 123
bgp router-id 3.3.3.3
no auto
no syn
neighbor 2.2.2.2 remote-as 123
neighbor 2.2.2.2 update-souce lo0
neighbor 5.5.5.5 remote-as 5
neighbor 5.5.5.5 update-souce lo0
r5:
router bgp 5
bgp router-id 5.5.5.5
no au
no syn
neighbor 3.3.3.3 remote-as 123
neighbor 3.3.3.3 update-souce lo0
默认ebgp ttl为1
r3:
neighbor 5.5.5.5 ebgp-multihop
r5:
neighbor 3.3.3.3 ebgp-multihop
r3:
ip route 5.5.5.0 255.255.255.0 35.1.1.5
r5:
ip route 3.3.3.0 255.255.255.0 35.1.1.3
bgp的network只是通告路由，必须本地路由表有的。
r4:
router bgp 4
net 4.4.4.0 mask 255.255.255.0
出现不优Bgp路由的情况：
1.同步开启（强制关闭同步）
2.下一跳是否可达
r2:
router bgp 123
neighbor 3.3.3.3 next-hop-self
r5:
router bgp 5
net 5.5.5.5 mask 255.255.255.255
net 3.3.3.3 mask 255.255.255.0
r3:
router bgp 123
neighbor 2.2.2.2 next-hop-self
