It does support SIP and more to the point it supports acting as an SBC by using the Cube functionality. You’d need to have Cube session licenses to stay within the scope of license infringement. However your platform is end of support since many years, so you would not be able to procure the needed license. You’ll be better of by using something more current, like an ISR 4K, which is soon to be EOS, or a Catalyst 8K router, that is the predecessor to the 4K platform.
For the configuration please see this document. Cisco Unified Border Element Configuration Guide Through Cisco IOS XE 17.5
I don’t know what E-gates is, but if it is as you state that your router is already acting as a SBC then I don’t see what you problem is, just configure the router to handle the SIP connection from your service provider. In my previous response I provided a link to the document you’d need to use your old router as a SBC for SIP.
I would absolutely not recommend you to have the SIP trunk setup directly to your CM.
If your 2900 is acting as an SBC and leveraging the CUBE feature on the IOS, you don’t need anything else.
I have a customer who terminated the SIP trunk from the ISP on a firewall and performed the NAT. They succeeded in this setup, but the firewall had to work hard to make it function. I’m not sure if they are still using this setup or if they have transitioned to a CUBE setup.
The recommended option is to use a router that has CUBE licenses where you terminate the ISP SIP trunk. This is the commonly used method.
We have advised you to upgrade to the latest hardware because the current hardware you are using has reached its end-of-life quite some time ago. Moreover, you cannot procure any additional CUBE licenses if needed, and furthermore, you won’t receive any support for the hardware.
I didn’t personally handle the firewall aspect. The team collaborated with the firewall vendor to get it operational, and I observed them facing significant challenges in this process.
You should consult with your firewall vendor for further assistance. As for the quote for the 4k router, I recommend reaching out to a local Cisco Partner who can provide the necessary support
You are welcome to post your running configuration in a text file and attach it to a response.
