BGP相对OSPF来说在骨干网络上使用的比较多，是目前域间路由协议的事实标准。通常在服务器上直接使用BGP的场景不多（内部网络大家都倾向使用OSPF这类IGP）。其实BGP的配置也很简单，从以下的拓扑来看4个机器的BGP配置
各路由配置文件
R1 配置
!
log file /var/log/quagga/zebra.log
log file /var/log/quagga/bgpd.log
!
password bgp
!
interface eth0
ipv6 nd suppress-ra
link-detect
!
interface eth1
ipv6 nd suppress-ra
no link-detect
!
interface lo
no link-detect
!
interface tunl0
ipv6 nd suppress-ra
no link-detect
!
router bgp 65000
bgp router-id 10.1.0.5
redistribute connected metric 121
neighbor 10.1.0.4 remote-as 65000
neighbor 10.1.0.4 password DOCKER
neighbor 10.1.0.4 next-hop-self
distance bgp 250 200 150
exit
!
access-list all permit any
!
ip forwarding
ipv6 forwarding ! line vty ! end
### R2 配置
log file /var/log/quagga/zebra.log log file /var/log/quagga/bgpd.log ! password bgp ! interface eth0 ipv6 nd suppress-ra link-detect ! interface eth1 ipv6 nd suppress-ra no link-detect ! interface lo no link-detect ! interface tunl0 ipv6 nd suppress-ra no link-detect ! router bgp 65000 bgp router-id 10.1.0.3 redistribute connected metric 121 neighbor 10.1.0.4 remote-as 65000 neighbor 10.1.0.4 password DOCKER neighbor 10.1.0.4 next-hop-self distance bgp 250 200 150 exit ! access-list all permit any !
ip forwarding
ipv6 forwarding ! line vty ! end
### R3 配置
log file /var/log/quagga/zebra.log log file /var/log/quagga/bgpd.log ! password bgp ! interface eth0 ipv6 nd suppress-ra link-detect ! interface eth1 ipv6 nd suppress-ra no link-detect ! interface lo no link-detect ! router bgp 65000 bgp router-id 10.1.0.4 redistribute connected metric 121 neighbor IBGP peer-group neighbor IBGP remote-as 65000 neighbor IBGP password DOCKER neighbor 10.1.0.2 remote-as 65001 neighbor 10.1.0.2 password DOCKER neighbor 10.1.0.2 ebgp-multihop 255 neighbor 10.1.0.3 peer-group IBGP neighbor 10.1.0.5 peer-group IBGP maximum-paths ibgp 32 distance bgp 250 200 150 exit ! access-list all permit any !
ip forwarding
ipv6 forwarding ! line vty ! end
### R4配置
log file /var/log/quagga/zebra.log log file /var/log/quagga/bgpd.log ! password bgp ! interface eth0 ipv6 nd suppress-ra link-detect ! interface eth1 ipv6 nd suppress-ra no link-detect ! interface lo no link-detect ! interface tunl0 ipv6 nd suppress-ra no link-detect ! router bgp 65001 bgp router-id 10.1.0.2 redistribute connected metric 121 neighbor 10.1.0.4 remote-as 65000 neighbor 10.1.0.4 password DOCKER neighbor 10.1.0.4 next-hop-self distance bgp 250 200 150 exit ! access-list all permit any !
ip forwarding
ipv6 forwarding ! line vty ! end
## BGP邻居状态
R3与其他节点都是邻居，因此以R3的为例
c78df8a1d9d5# show ip bgp neighbors BGP neighbor is 10.1.0.2, remote AS 65001, local AS 65000, external link BGP version 4, remote router ID 10.1.0.2 BGP state = Established, up for 01:33:01
Last read 00:00:01, hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities: 4 Byte AS: advertised and received
Route refresh: advertised and received(old & new)
Address family IPv4 Unicast: advertised and received
Graceful Restart Capabilty: advertised and received
Remote Restart timer is 120 seconds Address families by peer: none Graceful restart informations: End-of-RIB send: IPv4 Unicast End-of-RIB received: IPv4 Unicast Message statistics: Inq depth is 0 Outq depth is 0 Sent Rcvd Opens: 1 1 Notifications: 0 0 Updates: 5 2 Keepalives: 95 94 Route Refresh: 0 0 Capability: 0 0 Total: 101 97 Minimum time between advertisement runs is 30 seconds
For address family: IPv4 Unicast Community attribute sent to this neighbor(both) 3 accepted prefixes
Connections established 1; dropped 0 Last reset never External BGP neighbor may be up to 255 hops away. Local host: 10.1.0.4, Local port: 36686 Foreign host: 10.1.0.2, Foreign port: 179 Nexthop: 10.1.0.4 Nexthop global: :: Nexthop local: :: BGP connection: non shared network Read thread: on Write thread: off
BGP neighbor is 10.1.0.3, remote AS 65000, local AS 65000, internal link Member of peer-group IBGP for session parameters BGP version 4, remote router ID 10.1.0.3 BGP state = Established, up for 01:32:57
Last read 00:00:57, hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities: 4 Byte AS: advertised and received
Route refresh: advertised and received(old & new)
Address family IPv4 Unicast: advertised and received
Graceful Restart Capabilty: advertised and received
Remote Restart timer is 120 seconds Address families by peer: none Graceful restart informations: End-of-RIB send: IPv4 Unicast End-of-RIB received: IPv4 Unicast Message statistics: Inq depth is 0 Outq depth is 0 Sent Rcvd Opens: 2 0 Notifications: 0 0 Updates: 3 2 Keepalives: 94 93 Route Refresh: 0 0 Capability: 0 0 Total: 99 95 Minimum time between advertisement runs is 5 seconds
For address family: IPv4 Unicast IBGP peer-group member Community attribute sent to this neighbor(both) 4 accepted prefixes
Connections established 1; dropped 0 Last reset never Local host: 10.1.0.4, Local port: 179 Foreign host: 10.1.0.3, Foreign port: 43991 Nexthop: 10.1.0.4 Nexthop global: :: Nexthop local: :: BGP connection: non shared network Read thread: on Write thread: off
BGP neighbor is 10.1.0.5, remote AS 65000, local AS 65000, internal link Member of peer-group IBGP for session parameters BGP version 4, remote router ID 10.1.0.5 BGP state = Established, up for 01:32:56
Last read 00:00:56, hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities: 4 Byte AS: advertised and received
Route refresh: advertised and received(old & new)
Address family IPv4 Unicast: advertised and received
Graceful Restart Capabilty: advertised and received
Remote Restart timer is 120 seconds Address families by peer: none Graceful restart informations: End-of-RIB send: IPv4 Unicast End-of-RIB received: IPv4 Unicast Message statistics: Inq depth is 0 Outq depth is 0 Sent Rcvd Opens: 2 0 Notifications: 0 0 Updates: 3 2 Keepalives: 94 93 Route Refresh: 0 0 Capability: 0 0 Total: 99 95 Minimum time between advertisement runs is 5 seconds
For address family: IPv4 Unicast IBGP peer-group member Community attribute sent to this neighbor(both) 4 accepted prefixes
Connections established 1; dropped 0 Last reset never Local host: 10.1.0.4, Local port: 179 Foreign host: 10.1.0.5, Foreign port: 42140 Nexthop: 10.1.0.4 Nexthop global: :: Nexthop local: :: BGP connection: non shared network Read thread: on Write thread: off
## 各节点上的路由表
1. R3上ECMP路由
default via 172.19.0.1 dev eth1 10.1.0.0/16 dev eth0 proto kernel scope link src 10.1.0.4 100.100.100.1 via 10.1.0.5 dev eth0 proto zebra metric 20 100.100.100.2 via 10.1.0.3 dev eth0 proto zebra metric 20 100.100.100.4 via 10.1.0.2 dev eth0 proto zebra metric 20 100.100.100.100 proto zebra metric 20 nexthop via 10.1.0.5 dev eth0 weight 1 nexthop via 10.1.0.3 dev eth0 weight 1 172.18.0.0/16 via 10.1.0.5 dev eth0 proto zebra metric 20 172.19.0.0/16 dev eth1 proto kernel scope link src 172.19.0.2
## 其他说明
1. 本测试中用了peer group，主要是IBGP内多个邻居测试比较简单一些。
2. quagga内默认IBGP的路径最大是1，通过maximum-paths ibgp 32改了一下。
3. 本案例中R1和R2是不通的，因为IBGP内未做特殊设置(BGP反射或者BGP联盟)是不会接受其他IBGP邻居传递的路由。
4. 要想能从R4访问R1/R2宣告的100.100.100.100/32需要注意linux的kernel版本。。3.10的版本是按每个包单独转发，是建立不了TCP连接的。我测试时升级到了4.4.
## 参考文档
1. https://lwn.net/Articles/656111/