Port forwarding between two Cisco Devices

[SABER3990]

Hello my name is Yoel

I have two service providers AT&T and Comcast Network, and one main router, Cisco rv042 dual wan. I need to forward some services over TCP Ports (80,443) AT&T uses "2Wire 3801HGV" and Comcast uses "Cisco DPC3939B". Now I am currently using AT&T modem without any problems, it forwards all services to my main router(RV042) and the router to my machines in my network. But with Comcast Business Gateway it has been impossible so far, the configuration is as easy as 1,2,3, but when I test my ports, 80 is open but it never gets to the main router, I have spoken to Comcast customer support several times and every time they tell me that all looks fine and that they don't have any restrictions to any ports. So, what can I do? Does anyone have some new idea. 

PD.When I run PFPortChecker and others tools in port 80 in both MODEMS I get this reply: your port is Open, Differences? Yes, AT&T WORKS COMCAST DOESN'T!!!.

I think that could be some communication issue between both Cisco devices?

Can I help me Please.

Thanks

[mdobiac · Accepted solution]

Hello Saber3990,

For your Comcast side of the connection is the RV042 getting a public IP address from the modem?

If not then the Double NATing for that connection could be part of the problem.  Otherwise check your Inbound table (make sure you enable Allowed connections in your logs) to see if the request is even getting to the RV042.

If you have any other questions please let us know.

Thank you,

Michael D.

If this post if helpful please rate or mark as correct.

[SABER3990]

Hello Thanks Michael

No The RV042 is getting a private from Comcast modem. I enabled the port forwarding in Cisco DPC3939B  to the RV042. I think as you tell me that the double Nating could be the problem,  but the AT&T side is the same configuration of double Nating and works great, then could be some conflict between both cisco devices.

I am uploading some pictures of my real configuration (both modems and the router) and one network map of my internal network.

As you can see in both modems there is one device connected only (the RV042) and all ports are pointing to RV042 and this to my servers. ATT works fine Comcast doesn't.

I appreciate you help I need to get running that configurations.

Thank you very much.

Yoel