D-Link DES-3326SRM Product Manual - Page 168
OSPF Cost, Shortest Path Tree, The formula used to calculate the OSPF cost is as follows
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D-Link DES-3326S Layer 3 Switch OSPF Cost Each OSPF interface has an associated cost (also called "metric") that is representative of the overhead required to send packets over that interface. This cost is inversely proportional to the bandwidth of the interface (i.e. a higher bandwidth interface has a lower cost). There is then a higher cost (and longer time delays) in sending packets over a 56 Kbps dial-up connection than over a 10 Mbps Ethernet connection. The formula used to calculate the OSPF cost is as follows: Cost = 100,000,000 / bandwidth in bps As an example, the cost of a 10 Mbps Ethernet line will be 10 and the cost to cross a 1.544 Mbps T1 line will be 64. Shortest Path Tree To build Router A's shortest path tree for the network diagramed below, Router A is put at the root of the tree and the smallest cost link to each destination network is calculated. Figure 23- 1. Constructing a Shortest Path Tree 158
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