Cisco has online tools to help designers make the proper selection of devices and uplink
ports based on business and technology needs. Some suggested oversubscription ratios that
you can use to plan bandwidth requirements between key devices on a network with
average traf?¬?c ?¬‚ows are as follows:
?– Access to distribution layer links: The oversubscription ratio should be no higher
than 20:1. That is, the link can be 1/20 of the total bandwidth available cumulatively to
all end devices using that link.
Improving Performance with Spanning Tree 43
?– Distribution to core links: The oversubscription ratio should be no higher than 4:1.
?– Between core devices: Little to no oversubscription should be planned here. That is,
the links between core devices should be able to carry traf?¬?c at the speed represented
by the aggregate-number bandwidth of all the distribution uplinks into the core.
EtherChannel Overview
The increasing deployment of switched Ethernet to the desktop can be attributed to the
proliferation of bandwidth-intensive applications. Any-to-any communications of new
applications, such as video to the desktop, interactive messaging, and collaborative whiteboarding,
increase the need for scalable bandwidth.
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