SIP trunk between two CUCM question

[sindan]

How can  be two CCM clusters be connected together using a SIP trunk? They are not on the same network thus a inter cluster trunk cannot be used.  Thanks,

[Roman Rodichev]

If there is IP reachability between two CM clusters, you could build a direct SIP trunk, why not?

But the preferred method is to use a voice gateway, also known as IP-to-IP gateway, or Session Border Control (SBC), or by its new term Cisco Unified Border Element (CUBE). It requires CUBE license. You would configure "voice service voip" and allow SIP to SIP connections. The rest is taken care of by dial-peers.

[sindan]

There is no IP connectivity between the clusters. Is there anything else needed to be purchased beside the CUBE license? Any SIP trunk service is necessary? How do the VGs learn about each other? Thanks,

[Roman Rodichev]

What do you mean that there is no IP connectivity between two clusters? Are you just saying that there are firewalls and NAT in between? You need some IP connectivity for SIP to work.

By the way, if you are on CallManager 8.0, you could take a look at Cisco Intercompany Media Engine (IME) solution: http://www.cisco.com/en/US/prod/collateral/voicesw/ps6788/vcallcon/ps10669/data_sheet_c78-601723.html

In regards to CUBE, you just need CUBE license for the IOS router. I imagine you would have two CUBE gateways, one on each side. You would have to setup SIP trunk between two CUBE gateways.

[sindan]

Thanks for your reply,

Yes, there are firewalls in between the clusters. Do I need to configure NAT on each side and assign each cluster an external IP or do the VGs require external IPs?

I am on CCM 4.2(3) on one side and 7.1.5(b) on the other side.

Please advise,

[Raees Shaikh]

The Voice GW would need an external IP inorder to enable reachability between the two GW`s. The basic point is that there should be reachability between the two clusters over IP network.

[sindan]

It totally makes sense that the clusters need to be reachable, however I  was told by a Cisco TAC engineer that the CUCM would need an external IP not the GW. I am still confused. Do you know any Cisco documentation where I can read further about this design/configuration?

Thanks,

[paolo bevilacqua · Accepted solution]

I  was told by a Cisco TAC engineer that the CUCM would need an external IP not the GW. I am still confused. Do you know any Cisco documentation where I can read further about this design/configuration?

That is incorrect. In fact, the point is not about externa or internal IPs, but simply IP connectivity as other mentioned already.

I recommend you engange a reputable consultant or certified Cisco partner for the design, otherwise you risk to go around and around without getting to a robust and effective solution.