Random slow connectivity - Help!!

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May 14th, 2008
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I'm suffering from random occurrances of slow connectivity that last for a few seconds and keep repeating every few minutes.

I've simply got 6 3560 switches two of which are doing routing via ospf. They simply route traffic out of our link to the datacentre. Can somoen please suggest what debugging procedures I can take.

So far I've done pings to our local switches, all of them suffer from losing packets, but so far our main switch which contains the LES link connection and is doing the routing hasn't suffered in our tests i.e hasn't had any packet loss.

Any thoughts?

Kind Regards


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shelgaonkar Thu, 05/15/2008 - 01:52
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Check the cpu utilization of the switches to find out which process is eating up the resources.(>show process cpu history;.show proc memory).

dan_track Thu, 05/15/2008 - 02:31
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I'd like some input with the following:

I believe I've found the problem, one of our avaya phones was plugged into the switch, but somebody had connected both the phone port and the data port into the network, instead of connecting a pc into the data port.

Any thoughts on why this would cause the intermittent slow connectivity and loss of packets?



smckenzie1 Thu, 05/15/2008 - 04:57
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Hi Dan,

It would seem that connecting the avaya phone back into the switch may cause a Layer 2 loop and therefore create a broadcast storm. Which in turn would drive up traffic loads and cpu load, hence packet loss. On recent experience using 3750s, we would have the port go into error-disable as is would see a BPDU by connecting the phon eback in.

To verify I would look at broadcast vs total traffic traffic on the interfaces of the switches that were connected to both side of the phone.

To stop this impacting I have ensured that BPDUguard is enabled and also strom control is enable on the user port.

This is based on my experience and hope this helps.

Regards Scott


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