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Because I am not very familiar with the MPLS technology, I would like to have some opinions about the following problem. I have attached a photo which describes the network.

1. You are the CSE and you are meeting with a customer that has a technical problem. Your customer has a central site with Call-manager, IP phones and 4 remote sites.

2. Each site connects to an MPLS/VPN via frame-relay between PE and CE. At the remote sites there are also IP phones. Each site has a 2M pipe towards the MPLS/VPN cloud. Every site (CE) has QOS configured.


? The customer complains about intermittent bad voice quality

? Help solve the customer?s problem.

Thank you in advance.


Re: VoIP on MPLS


First, it is not an easy task to find intermittend performance issues. Assuming you are using MQC for the QoS configuration, you can use "show policy-map interface " to get current QoS related counters. Especially watch out for dropped packets in the priority queue on both, PE and CE.

Also check with the customer, that call admission control only allows the number of calls supported by the priority queue on the WAN interfaces. If there is no indication of any drops, the problem might be found in the customer LAN, f.e. an overloaded trunk or access interface, where a phone is connected.

As a first approach use "auto qos voip" on all relevant ports (LAN switches and routers) i.e. where voip traffic can be found.

Last remark for now: you could setup IP SLA ( to continuously monitor the VoIP environment. This requires however some reconfiguration, maybe IOS upgrades and likely monitoring software.

Regards, Martin

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