Brodcast

[Ibrahim Jamil]

Hello Folks!

sh int g1/1 shows me the below brodcast,is that normal?how to troubleshoot?

Received 132532351 broadcasts, 0 runts, 0 giants, 0 throttles

[Latchum Naidu]

HI,

This is not normal broadcast,

You need to identify which is connected on that port and if it is PC then identify which application is generating more broadcst.

May be any application or virus can generate more broadcast.

Try to findout that PC and have virus scan on that.

Please rate the helpful posts.

Regards,

Naidu.

[Ibrahim Jamil]

Hi

Any troubleshooting Methdology

[Latchum Naidu]

Hi,

See the below link to troubleshoot...

http://support.3com.com/infodeli/tools/netmgt/tncsunix/product/091500/c9bstorm.htm

And ultimately you need to identify the PC which is connected to that interface and do the necessary steps like find out which application generating the broadcast and do virus scan like that...

Please rate the helpfull posts.

Regards,

Naidu.

[IAN WHITMORE]

Well first off, you have a lot of braodcasts but over what time span? Maybe it's normal.

Is link g1/1 an uplink to another switch? Or to a PC/Server? If it's an uplink to another switch you need to trace back on the next switch by looking at the ports one by one (although you can filter the output using the pipe | command to see all the broadcast counters quickly) to see if there is another port with extremely high broadcasts (in a short time span)...then it's just a case of repeating the process until you find the guilty party.

Regards,

Ian

[George Stefanick]

You could "port span" the port and put wireshark on it ... You will see 255.255.255.255, which is broadcast ... You will see the sourse of who is sending it ...

[George Stefanick]

Here is how to port span ...

http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a008015c612.shtml

[Ibrahim Jamil]

Thanks George,Thanks Guys

[hegegabor]

Hi,

Is the unicast traffic flows normaly?

when ping something on your lan network is it comes back normally?

In many cases it is because there is a loop on your network.

If the network becomes slow it could be the problem.

to resolve the loop problem, use the bpdu guard:

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a008009482f.shtml

if a port goes error disable when you apply the bpduguard, you have a loop on your network,

then try to remove the loop physically.

regards,

Gabor

/please vote if this resolves the issue/

[Ibrahim Jamil]

Hi Gabor

How to remove the loop Physicaly?

[hegegabor]

remove the cable if you find the loop

Have you got a slow-down on your network?

it could be a broadcast storm. The broadcast message is sent out on all interfaces of the switch (except the source int), and if you have a loop, the packet never stops, circulate on the network (no time to leave - TTL), broadcast countesr goes very high.

if you set the portfast on the access ports (end devices connects there), BPDU sould not be seen on that port. So if you see BPDU then there is a loop. Bpduguard helps you to find that BPDU packets.

enable bpduguard and check port goes down.

don't forget portfast.

regards Gabor.

[Ibrahim Jamil]

Hi

So i need to enable BPDU Guard on just the interface where the brodcast is?

regarding remove cable i can't cause this is a production server

that is magic my network Its Performing well and Specialy for this server holds application responds quickly

[Latchum Naidu]

Hi,

Yes, once you enable BPDU guard on the specific interface then you will be stoping broadcast which will increase the performance.

Below is the sample config for you...

interface FastEthernet0/25
switchport mode access
shutdown
storm-control broadcast level 5.00
storm-control multicast level 5.00
spanning-tree portfast
spanning-tree bpdufilter enable
spanning-tree guard root

You can set various broadcast level it completely depends how you want and control.

Please rate the helpfull posts.

Regads,

Naidu.

[Ibrahim Jamil]

Thanks