Connect to SIP provider via ASA

[Zhomart Asken]

Hi everybody! In near future our company is going to subscribe to SIP services, but i'm not sure how it will work through ASA firewall. I heard that NAT causes problems for sip telephony. What kind of minimum configurations should i make on ASA to allow sip to function properly? 

[adawa]

Hello, ZhomartCisco.

Is this for your existing ASA appliance (what model and version?), let me see what reference can help you. 

Let me know if you have additional concerns or e-mail (adawa@cisco.com) me directly. Kind regards. 

[Zhomart Asken]

Thanks for reply. Yes it is for existing ASA appliance. Model is 5510 and version i hope 8.2(not at work right now). Any information would be appreciated.

Best wishes

[mmoulson1]

Just ensure you disable SIP inspection on your ASA, this can cause problems as it can modify the SIP messages.

You didn't say what call platform you are using? CUCM etc? Are you planning to pass the SIP trunk to an Cisco router running CUBE? Or directly to you PBX?

Matty

[Zhomart Asken]

Thanks! We are using avaya for telephony. We don't have a router running CUBE, so i guess directly to PBX. But i heard that inspection should be enabled, so it can translate the private address of sip to public(to avoid one way audio problem)? Could you you explain

[mmoulson1]

I would check that your Avaya can support the required SIP parameters for the provider. Certainly in my experience every SIP provider seems to do things slightly differently!

With regard to the inspection I guess you can try and see. It's just a check box for on/off on the ASA and you'll soon find out if it works or not! Again in my experience it needs to be turned off! I have recently worked on a few installs of Mitel systems using SIP behind ASA and the SIP inspect caused one way audio!

Good luck!

Matty

[Zhomart Asken]

To be correct version of software is asa842-k8.bin. Thanks