究竟什么是NBMA

NBMA早在CCNA中就有所接触,只是一直对这个名字没有什么概念,这也许应该说是翻译惹的祸,毕竟他翻译后面没有加个括号写一下英文对应的名字……嗯,至少没有写全称。所以,如果我换做来说非广播多路访问的时候你就知道了,没错,NBMA就是非广播多路访问的简称。

全称是non-broadcastmultipleaccess,与之对应的就是MBA,自然也就是broadcastmultipleaccess,即广播多路访问,这个名词应该是早在第一次接触帧中继的时候了解到的。在帧中继中默认是不能发送广播的,在OSPF协议中,对这些网络划分了类别,比如NBMA(正式提出是作为OSPF协议的一种网络类型),比如点对点,比如虚链路等等。

在后来的高级书中都直接说NBMA,其实就是非广播多路访问,简单理解,现在还在应用的也就是帧中继了。。。

哦对了,一般是没有MBA的说法的哈~

下面给出原文:

NBMA (non-broadcast multiple access)is one of four network types in the OSPF (Open Shortest Path First) communications protocol. NBMA is used to accurately model X.25 and frame relay environments in multiple-access networks where there are no intrinsic broadcast and multicast capabilities. The other OSPF network types are: broadcast, point-to-point, and point-to-multipoint. In an NBMA configuration, OSPF sends HELLO packets (packets sent periodically to establish and confirm neighbor relationships between routers) to each router one at a time rather than multicasting them. The HELLO timer (which tells the router how often to send HELLO packets) is extended from 10 to 30 seconds and the dead router timer (which tells the router how long to wait before it decides that a neighboring router is not functioning) is extended from 40 to 120 seconds.

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