Wandering's Blog » 日志 » BGP :: 发现一个有意思的东西
BGP :: 发现一个有意思的东西
Wandering 发表于 2008-04-24 20:27:58
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好像没有人注意过这件事哦……呵呵 (Routing TCP/IP, volume II)
Example 3-16 Configuring Taos with the network Command
router eigrp 200
passive-interface Serial0
network 192.168.1.0
network 192.168.100.0
!
router bgp 200
network 192.168.1.216 mask 255.255.255.252
network 192.168.100.0
network 192.168.200.0
neighbor 192.168.1.226 remote-as 100
The major networks 192.168.100.0 and 192.168.200.0 are specified alone. For the subnet 192.168.1.216, a mask is also specified. Subnets and masks can be specified only under BGP-4; under EGP or earlier versions of BGP, all of which are classful, only major networks can be specified.
Notice that the no auto-summary command is not used under either EIGRP or BGP in this configuration. Because no redistribution is taking place, turning off auto-summarization is unnecessary. Example 3-17 shows the result of the configuration.
解释一下上面内容的主要意思吧，其实最关键就是最后一段的第 2 句话。Because no redistribution is taking place, turning off auto-summarization is unnecessary.
什么意思？第一层意思是字面意思，所表达的第二层意思是，BGP 的 auto-summary 只是对 redistribute 进 BGP 的 IGP 路由进行汇总，如果使用 network 将 IGP 路由发布到 BGP 中，auto-summary 是不会对这些路由汇总的。不相信？做实验吧，我测试过，的确如此。
因此，在实际工作中，不管三七二十一上来就把 BGP 的 auto-summary 关掉，到不一定是错误的，但或许很多人都不是真正地明白为什么要这样做。话说回来，我就真正的理解了吗？不见得。总之，共勉吧……
...
好像没有人注意过这件事哦……呵呵 (Routing TCP/IP, volume II)
Example 3-16 Configuring Taos with the network Command
router eigrp 200
passive-interface Serial0
network 192.168.1.0
network 192.168.100.0
!
router bgp 200
network 192.168.1.216 mask 255.255.255.252
network 192.168.100.0
network 192.168.200.0
neighbor 192.168.1.226 remote-as 100
The major networks 192.168.100.0 and 192.168.200.0 are specified alone. For the subnet 192.168.1.216, a mask is also specified. Subnets and masks can be specified only under BGP-4; under EGP or earlier versions of BGP, all of which are classful, only major networks can be specified.
Notice that the no auto-summary command is not used under either EIGRP or BGP in this configuration. Because no redistribution is taking place, turning off auto-summarization is unnecessary. Example 3-17 shows the result of the configuration.
解释一下上面内容的主要意思吧，其实最关键就是最后一段的第 2 句话。Because no redistribution is taking place, turning off auto-summarization is unnecessary.
什么意思？第一层意思是字面意思，所表达的第二层意思是，BGP 的 auto-summary 只是对 redistribute 进 BGP 的 IGP 路由进行汇总，如果使用 network 将 IGP 路由发布到 BGP 中，auto-summary 是不会对这些路由汇总的。不相信？做实验吧，我测试过，的确如此。
因此，在实际工作中，不管三七二十一上来就把 BGP 的 auto-summary 关掉，到不一定是错误的，但或许很多人都不是真正地明白为什么要这样做。话说回来，我就真正的理解了吗？不见得。总之，共勉吧……
...
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