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The Cisco router in my organisation is set up to use Port Address Translation (PAT) for Internet connectivity.


All outbound internet connections are from the ip address or the border Cisco interface, and mapping to internal addresses is based on ports.

My understanding is that Peer to Peer applications like Skype have difficulty with PAT, and when they can't establish a direct Peer to Peer connection between clients, the Skype protocol starts to relay connections between 3rd party hosts. I can see this behaviour in the Skype Technical Call Info during calls:

UDP status is reported as "Bad" and the number of relays in play can range from between 1 to 4.

This obviously impacts on Skype performance.

I wanted to ask 2 things:

Is there an optimal way to configure PAT on a Cisco router to make things easier for Skype?

At the moment, I just use the standard:

ip nat inside source list nat-list interface GigabitEthernet0/0 overload

If this is as good as it gets, what are my options?

I was thinking about creating a dedicated Socks Proxy for Skype and created a dedicated NAT translation for that using one of our spare public ip addresses.

Does that sound like a plan?

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