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Faulty PC NIC on one PC causing packet loss throughout the whole network

kasper123
Level 4
Level 4

We have a network of arround 40 switches. Several stacked 3750 switches as core and the rest are 3750 and 2960 access switches.

Today we noticed packet loss and ping drops occuring throughout the network. We narrowed down the problem to a single switch and then to a single port on that switch. On that port there was a PC that was in standby that was causing the outage. After removing the PC the problem went away. We made sure it is the PC that was causing the problem by connecting a different PC on that port (and cable) and also connecting the faulty PC on another port.

The port where the PC was connected had CRC errors.

My question is what could have happened? How could the PC bring down the whole network? Is there something we can do to prevent that in the future? Is there a way for the switch to send an SNMP Trap when CRC errors occur on a port?

 

Regards.

5 Replies 5

acampbell
VIP Alumni
VIP Alumni

Hi,

This sounds more like you have been hit with
flooding IE a broadcast or unicast storm.

Please have a look at this section of the 3750 config guide.

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/12-2_55_se/configuration/guide/scg3750/swtrafc.html#wp1038435

Regards
Alex

 

Regards, Alex. Please rate useful posts.

Thank you Alex!

Is it a best practice to implement storm control on all ports of a switch or only on the uplinks? Are there any values that are considered best practice values for a gigabit link? 

Does this impact the CPU of the switch?

Regards.

Hello

 

storm control is an access port feature, I wouldn't advise applying it to switch interconnects

res

Paul


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

Hello 

try this:

 

nt xx

Siwchport host

Spanning-tree bpduguard enable

Udld aggressive

Storm-controll broadcast 20

 

Res

paul


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

Hi,

Excellent advice from Paul (+5 P)

Included here is link to 6500 Best Practise.
http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SX/best/practices/recommendations.html

You can pick out features etc that are common to other switch models.


Regards
Alex

Regards, Alex. Please rate useful posts.
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