CUBE to ITSP via Public IP ?

[dineshshoba]

Can you also help me out for the below scenario.

CUCM - SIP -CUBE - SIP - ITSP

CUCM - CUBE -> configured the lan interface. Done the binding in the dial-peer

CUBE - ITSP -> configured the WAN interface. Done the binding in the dial-peer

Problem here is, the invite to the ITSP is going with the WAN interface and that should be the normal case.

But the ITSP is expecting the invite from our Public IP address which is different from our WAN int IP Address.

What could be the solution to resolve this issue. NATing needs to be done between my WAN interface IP and the Public IP ?

[TONY SMITH · Accepted solution]

What do you have between the gateway and the Internet?  From what you describe you do need NAT since the ITSP won't of course be able to reply to an internal IP address.  

Depending on the ITSP you may also need some static firewall rules to open ports, and you may or may not need to enable some sort of application level gateway function to fix up the SDP to match.   The most common configuration I've found I need is a static NAT, and firewall rule allowing UDP port 5060 inbound from the ITSP proxy to the gateway.   

[dineshshoba]

Hi Tony,

Thanks for the response.

We have configured the cube in the Internet router. The IP address configured in the WAN interface is a private IP address. So I doubt we need to do NAT between the WAN interface IP and the Public IP, niot sure.

Even if we does so, will the SIP invite will change from WAN interface IP to Public IP  and reach the ITSP ?

[TONY SMITH]

I'm not clear on this bit "The IP address configured in the WAN interface is a private IP address", but you say that the ITSP is expecting to see your Public (Internet) IP address.  Maybe a bit more description of the installation would help, does your route to the ITSP go over the Internet, or do you have a private connection? 

[dineshshoba]

Hi Tony,

The configurations are done in the Internet router. The traffic is going via Internet.

[Mikolaj Moryto]

Hi,

Do you mean you use that router for both internet access and CUBE?

If so, there must be a device between your router and internet which does the NAT translation to public IP addresses. Configuration required on that device depends on its capabilities. One of the options may be to configure a static 1:1 NAT on that device.

Thank you,

Mikolaj

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[TONY SMITH · Accepted solution]

Hi,

In that case your Internet router should doing the required NAT.  However there are also some SIP specific considerations as well.   These will depend on the exact requirements of the ITSP, however ...

(1) You may need to have inbound port 5060 open in the firewall, restricted to traffic from the ITSP's gateway to your CUBE's Internet address. 

(2) You may need to enable or disable SIP ALG on the Internet router.  The specifics depend on the model of router or firewall, but essentially this function re-writes the SIP packets so that any internal reference to IP address is also converted to the public address.  Some ITSP's ask for this to be disabled.

(3) You may need other inbound ports open from ITSP to CUBE.

We can't really be more explicit without knowing what fault you're experiencing, is it complete failure or something specific like not hearing ringback, or one-way audio?  Can you post any debugs or packet captures? 

By the way you've marked the post as "fixed" but I don't think that's the case yet.

[dineshshoba]

Hi Tony,

Thanks for your post. Problem here is we don't have a firewall between our Cube and ITSP. The Natting needs to be done from ITSP side. We have decided to configure the PUBLIC IP directly on our router . Still working with ITSP.

[dineshshoba]

Hi Folks - We started receiving calls after configuring the PUBLIC ip directly on our internet router. 

Thanks for your suggestions.