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

1545 pts.
Tags:
Broadcast
Cisco
Networking
Switches
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 this 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?

Answer Wiki

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If all you are using is a network hub, then pretty much any network switch will be better than what you have now. Cisco makes top-end equipment which runs much of the Internet.

Added by Sudhanshu Gupta:

Hi,
I’m a routing and switching expert on SearchNetworking.com’s Ask the Expert panel. To answer your question, broadcasting means that the packets are received by each active host on the network. So whichever network interface card (<a href=”http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212660,00.html”>NIC</a>) 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 (<a href=”http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214184,00.html”>TTL</a>) 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.

Added by ####kb3cgj######

Which switch to get is dependent on the amount of traffic you need to switch. If you only have a 10Mbit internet connection then just about any switch will do. If you plan on growing, then getting a managed layer 3 cisco switch would be good. However, I recommend HP Procurve series switches…Lifetime warranty, Easy Web Interface, but the command-line works just like Cisco IOS. Awesome switches.

Nick

added by ****labnuke99****
The original question had to do with timeouts and issues with that and broadcasts. The broadcasts may be stopped by adding the switch but that is not necessarily going to stop the timeouts. Timeouts are just what they say, the packet did not make the round trip in the pre-defined timeframe. This could be because:

a. The link is indeed busy with broadcasts. However, broadcasts should not traverse a WAN link and should just stay on the local LAN. If the LAN is busy with excessive broadcasts, something is causing that and should be investigated. Use Wireshark or Microsoft’s Network Monitor 3.1 to capture packets and see what systems/services are generating the broadcasts.

b. The destination host is busy handling other client requests and too much time passes before it can respond to the ping request.

c. There are too many hops between the source and destination.

d. The link is down and there is not a path from the source to the destination.

With regards to B & C, you can play around with the ping parameters in Windows (and linux too). For Windows, ping has these options:
Usage: ping [-t] [-a] [-n count] [-l size] [-f] [-i TTL] [-v TOS]
[-r count] [-s count] [[-j host-list] | [-k host-list]]
[-w timeout] target_name

Options:
-t Ping the specified host until stopped.
To see statistics and continue – type Control-Break;
To stop – type Control-C.
-a Resolve addresses to hostnames.
-n count Number of echo requests to send.
-l size Send buffer size.
-f Set Don’t Fragment flag in packet.
-i TTL Time To Live.
-v TOS Type Of Service.
-r count Record route for count hops.
-s count Timestamp for count hops.
-j host-list Loose source route along host-list.
-k host-list Strict source route along host-list.
-w timeout Timeout in milliseconds to wait for each reply.

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