diff --git a/d36-EIGRP.md b/d36-EIGRP.md index 1ae893f..9c751a2 100644 --- a/d36-EIGRP.md +++ b/d36-EIGRP.md @@ -956,4 +956,12 @@ Routing entry for 172.16.100.0/24 基于表36.4中的信息,路由器R1将选择经由R4的路径,作为后继路由,这是根据该路由的可行距离得出的。此路由将被放入到IP路由表以及EIGRP拓扑表中。路由器R1随后将对那些到`192.168.100.0/24`网络的替代路径进行查看。这里邻居路由器R3到`192.168.100.0/24`网络的度量值,又被叫做是报告的距离或通告距离,就是10。该距离小于(当前的)可行距离,所以该路由满足到可行条件(FC),那么就被放入到EIGRP的拓扑表中。而邻居路由器R2到`192.168.100.0/24`的度量值为30。该值高于了当前的可行距离25。此路由则不能满足可行条件,就不被看作是一个可行后继(FC)。但该路由仍然会被放入到EIGRP的拓扑表中。这将在后面的EIGRP拓扑表小节,进行演示。 +当某个邻居路由器改变了度量值,或拓扑发生了改变,以及后继路由被移除或改变时,弥散更新算法会检查那些可行后继路由器的路由,在发现了一台可行后继路由器时,弥散更新算法就使用该可行后继路由器,以避免不必要的重新计算路由。执行一次本地运算,节省了CPU处理能力,因为在当前后继或主路由失效时,可行后继路由本身就已选出且已经存在了(When a neighbor changes a metric, or when a topology change occurs, and the Successor route is removed or changes, DUAL checks for FSs for the route and if one is found, then DUAL uses it to avoid re-computing the route unnecessarily)。此过程就叫做本地运算(local computation. This is referred to as local computation. Performing a local computation saves CPU power because the FS has been chosen and already exists before the Successor or primary route fails)。 + +而当目的网络的可行后继路由器不存在时,本地路由器将向邻居路由器发出一次查询,对邻居路由器是否有着关于目的网络的信息。如邻居路由器有该信息,同时另一路由器确实有着到目的网络的路由,此时该路由器将执行一次弥散运算(a diffusing computation),以确定出一台新的后继路由器(If the information is available and another neighbour does have a route to the destination network, then the router performs a diffusing computation to determine a new Successor)。 + +##EIGRP的拓扑表 + +**The EIGRP Topology Table** +