VLAN Traffic Monitoring

[caijunjie]

Hi all

I have a 2900XL core switches which in turn connected to several 2950 switches. All are connected to VLAN 1.

I have a few questions:

When people say broadcast traffic should not be more than 20% of the VLAN traffic.

1. Does it mean the broadcast of a single port in the 2950 switch or the core switch ?

2. How do i know the VLAN traffic ?

Any tools etc and how is the setup?

Hope comeone can help. :)

Thanks in Advance.

Alan

[jackyoung]

If there is VLAN, the broadcast mean within the VLAN because it will not travel outside the VLAN. If there is no VLAN then the broadcast will be in the whole network.

In normal case, the switch will not block the port if there is broadcast storm. You have to configure it. Please check below :

http://www.cisco.com/en/US/products/hw/switches/ps637/products_configuration_guide_chapter09186a008007e838.html

Could you explain more about the second question ?

[caijunjie]

Hi Jack

Thanks for your help. With regard to the second question, what I mean is

How do I monitor the VLAN and broadcat traffic respectively. What tool do i need.

I am using a 2900XL as my core switch and 2950 as my other switches.

Thanks in advance.

[gpulos]

an excellent tool for monitoring traffic would be a sniffer. (aka protocol analyzer)

http://ethereal.com has the best freeWare sniffer. with this tool, you can view each and every broadcast packet or just graph the percentage of broadcasts vs other types of traffic.....(many more features)

[caijunjie]

THanks, a question, if using a ethereal , how do I use it to monitor traffic on a particular VLAN

Thanks in Advance

[royalblues]

Hi

Connect a PC/laptop with the sniffer software and connect it to a port on the core switch 2900XL and span the VLAN. Your VLAN will your source traffic and the PC would be your destination.

Say if you want to capture vlan 2 statistics and you connect your PC to port 10, configure the following commands and start ethereal.

Monitor session 1 source vlan 2

monitor session 1 destination interface fa 0/10

HTH

Narayan

[caijunjie]

Thanks for the reply. Do I have to setup anything on the Ethereal. Any parameter to configure?

Someone please help. Thanks

[royalblues]

Just plug the laptop and start the application

It will start the capture.

Capture for about 5 minutes and analyse

HTH

Please rate useful posts

Narayan

[guruprasadr]

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Thanks & Regards,

Guru Prasad .R

[royalblues]

Hi Guru,

This is not the right forum to post these questions.

Narayan

[caijunjie]

Hi, thanks for your reply. From the packet capture, how do i know which one is my vlan traffic. I have only vlan 1.

THnaks in advance for your advice as i am not very good in traffic analysing.

Regards

Alan

[royalblues]

Hi Alan,

If you have only one vlan, this is your VLAN traffic.

HTH

Narayan

[caijunjie]

Hi Narayan

Thanks for all your kind and patience help. I will try and past again if I have any problem. Thanks again.

Regards

Alan