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Tips to find root cause of problem


Userlevel 1
latency of some computer in one specific vlan, Not all of the computers are affected, but it is increasing... checking traffic on ports, no messages on Core. If I move the pc to a different vlan the problem is solved for that computer, but still happening on the vlan. Please help

4 replies

Userlevel 2
Have you checked for:
- port error counters
- client side error counters
- counters in general

What does a tcpdump from a client show?
How are you measuring the latency and how much of a change are you measuring?
Userlevel 1
Yes... I check.. but nothing.. on the counters all normal, but a did a sh fdb port on all the ports in the affected vlan... and found a switch connected, as soon I disable the port the other pc's normalize... now we need to check if it is the switch or a pc connected to it generating the traffic...

Thanks
Userlevel 2
🙂 I suspect your network was looped with that other switch and you were encountering a broadcast storm. This would be apparent in a tcpdump from the client; you'll see the same broadcast packet appear in the dump multiple times. Have you enabled erp on the switch? I think it's erp; erp will automatically shutdown ports when it detects a loop.
Userlevel 4
Robert Cummins wrote:

:-) I suspect your network was looped with that other switch and you were encountering a broadcast storm. This would be apparent in a tcpdump from the client; you'll see the same broadcast packet appear in the dump multiple times. Have you enabled erp on the switch? I think it's erp; erp will automatically shutdown ports when it detects a loop.

ELRP - Extreme Loop Resolution Protocol
https://gtacknowledge.extremenetworks.com/articles/Q_A/What-is-ELRP/

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