3com 500 Manual De Usuario

 

 

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With only a single physical path between LANs, the network is susceptible 

 

to link and bridge failures. In the event of a failure, the connection between 

 

any of the LANs upstream or downstream of the point of failure will be 

 

broken. A more resilient network of interconnected LANs can be 

 

established by providing more than one link between any two of the LANs. 

 

Normally, this network would soon encounter serious problems 

 

resulting from a loop, around which frames could endlessly travel if 

 

precautions aren’t taken by the bridges. Over ISDN links a proprietary 

 

form of loop control is implemented. 

 

On startup, the bridges send out frames to enquire if there are other 

 

bridges on the network. By exchanging information, the bridges block 

 

ports that cause the loops and ensure that there is only ever one active 

 

path through the network. If one of the links or bridges fail, the other 

 

bridges detect this and reconfigure their ports so that there is once 

 

again an active data path through the network.

 

 

If your network topology is star shaped, a combination of ISDN and 

 

bridging is usually the most efficient and successful option. Routing is a 

 

better solution if your network topology is a complex mix of both 

 

leased line and ISDN circuits, running at 64 Kbps to 2 Mbps.

 

 

Bridges are programmed to automatically forward data packets by 

 

default while routers filter data packets by default. These attributes have 

 

an impact on the overall flow of data across the network. Much has been 

 

made of 

 

 in connection with bridged networks, where the 

 

broadcast signals from bridges propagate to fill all of the wide area 

 

bandwidth, and bring the network down. Broadcast storms cannot be 

 

attributed to installation of bridges or routers, but by poor protocol 

 

implementation and network design. However the deployment of routers 

 

can effectively 

 

 one logical network from another.