Cisco ASA, NAT and priority

We have a Cisco ASA 5510 firewall and everything is working good. We have a 20 MB fiber connection to the internet, so I didn’t setup a VLAN for the phones. I would like to change it so the SIP traffic gets the priority, but we are using NAT, and when I look at the packets going through the system, nothing is hitting SIP. I even closed the 5060 SIP port from incoming traffic and the phones still worked. How is the phone system working, and how do I prioritize the phone data leaving the ASA?

Just a little hint. We had a similar problem on our Cisco ASA. For some odd reason it takes the ASA about 10 minutes before it stops SIP packets from coming in. When we close port 5060 I can make calls for 10 minutes and then it starts blocking packets.

I don’t quite understand your question about QoS.
We have made a VLAN and gave that the highest priority (QoS). Next we programmed our Linksys SPA942 phones to get in that VLAN (it’s a default option in the Linksys menu).
Not sure if that helps but hope it can get you some further.

What I need to know is it possible to use QOS to prioritize VOIP traffic when everything in on the same VLAN? And why am I not seeing any SIP traffic going through the ASA, when the phones are working fine? I’m sure it has to do with NAT, but how does that work?

You will not be able to prioritize the SIP traffic going out to the Internet. There is no QoS on the Internet.

Are you using SIP trunking over the Internet? You will not see phone to phone traffic (internal calls) as SIP traffic on your router. That traffic will stay local to your switch. The only time you might see SIP traffic on the router is if you are making a call from a phone out to a SIP trunk that goes out your Internet connection.