Q

What is broadcasting and which switch will fix timed-out requests?

Broadcasting is defined by our routing and switching expert as he explains which network switch resolves time-out requests, in this response.

I am an Internet distributor of Exatt.net. When my customer pings the gateway it gives me lots of timed-out requests. Exatt.net says it broadcasts in your network. What does broadcast mean and how can I fix my timed-out requests? I use a hub. Someone told me to use a management switch, but I have no idea which switch is good. I don't know whether to use a Cisco second layer or third layer switch, or which model to use. What should I do?
Broadcasting means that the packets are received by each active host on the network. So whichever network interface card ( NIC) is listening will pick up and try to answer the packet. If they cannot answer, they will send it to their default gateway. Now it might happen that the default gateway and further gateways do not provide an answer before the time-to-live ( TTL) of the packet expires. So you will get a timed-out request. TTL is fixed so that packets do not remain on the network endlessly. Other reasons you might be getting time-out requests is because either a link is down in between the source and destination, or the host is too busy to answer.

You can configure the network to avoid sending time-outs but that's not a good idea as it is a measure to check

the performance of the network. The ideal way is to use expected ping to find out where the problem is and set it straight.

As for the second part of your question on how to control broadcast, hubs create a single collision as well as a broadcast domain. So a packet received on one interface is sent to all other interfaces whereas in a switch it depends upon the VLANs you create. A packet will go out of the certain port of the VLAN and not to all of the ports. Layer 2 switches will do simple switching whereas Layer 3 switches can do routing also. I would suggest you go for the Layer 3 switch. The price might be a little higher but you will have added functionality which will help you when you expand your network.

This was first published in May 2008

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