Broadcast on switch

[ankitzala]

How can we monitor the Broadcast on cisco 2900 switch and what are causes and resultion for that?

Thanks in advance.

[Georg Pauwen]

Hello,

are you experiencing too much broadcast traffic ? On the 2900 you can use the interface command ´port storm-control broadcast []´ to limit broadcasts. To find the source of your broadcasts it is best to use a sniffer, there are free ones available, like e.g. Ethereal, at www.ethereal.com.

Regards,

Georg

[ankitzala]

Thanks for your advice.even I am not sure about the amount of acceptable broadcast packaet on an interface.

Like right now I am getting 58 broadcast in 2 hours.

Do you think this is acceptable?

[Georg Pauwen]

Hello,

58 broadcast packets in 2 hours doesn´t sound like a whole lot. Obviously it depends, if you are experiencing slow traffic, it might be too much. I would check the txload (transmit) and rxload (receive) parameters (see the example below) on your interfaces to get an indication.

Switch#show interfaces FastEthernet0/1

FastEthernet0/1 is up, line protocol is up

Hardware is Fast Ethernet, address is 0004.c09a.f041 (bia 0004.c09a.f041)

MTU 1500 bytes, BW 0 Kbit, DLY 100 usec,

reliability 255/255, txload 4/255, rxload 7/255

HTH,

Georg

[scottmac]

Broadcasts are necessary as part of the TCP/IP spec (for Address Resolution Protocol - ARP - for example).

58 broadcasts in two hours is nothing. You have, like two or three machines on this LAN, right?

If you are getting "slow LAN" symptoms, do a show interface on each interface and examine the specs ... like you did to get the broadcast specs ... but watch for things like collisions, CRC errors, and "Late Collisions" - it is more likely a duplex mismatch or crappy cabling than broadcast overload.

Good Luck

Scott