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Beginner

QoS troubleshooting

Hello,

I have a client that is complaining about intermittent network congestion on their MPLS. The service provider has done their troubleshooting and can't see any issues. The client told me that it takes too long to send an email with large attachments and they feel they aren't getting the full bandwidth which was promised by the provider. I believe the issue could be related to QoS because it sounds like packets are being dropped when the network utilization is high.

I will be doing some wireshark captures (using a SPAN on the switch) at the demarcation for the MPLS drop to see what the potential issue could be. I may also have cli access to their switches (3850) to see if packets are being dropped.

I'm hoping for some suggestions or guidance to setup the wireshark captures and how best to troubleshoot using the CLI. I may need to have the captures run for a couple days so I mostly just need to know how to configure wireshark to only capture the headers.

I appreciate any help!

Thanks

3 REPLIES 3
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VIP Mentor

Hi

Sniffing the traffic to see if there are other issues is OK.

But, what type of traffic is sent when a confession is seen? It could be a qos or also for example a mtu issue, or other thing.

For QoS, do you know all queues the SP had setup. If yes i would do the following tests:

- using extended ping, I will setup a specific TOS value and validate that this value is kept at the other end.

- sending traffic with the right dscp value and using the maximum bandwidth authorized over the mpls to see that SP queues are inline with what agreed.

If QoS is fine then you can begin troubleshooting with wireshark internally to see what could be the issue.

Thanks

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Thanks
Francesco
PS: Please don't forget to rate and select as validated answer if this answered your question
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Thanks for the response Franscesco.

I will be working with the ISP beginning next week and will have the QoS configs from them to review before I do the captures.

Regards,

Waqas

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Ok. Let me know if you need more help.

Thanks

PS: Please don't forget to rate and mark as correct answer if this answered your question


Thanks
Francesco
PS: Please don't forget to rate and select as validated answer if this answered your question
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