How to Register to cucm 11 from external network

[hamadakhalaf]

Hello guys,

I'm trying to register with CUCM 11 from external netwrok using public IP , but the CUCM do not accept the registeration as it has  another IP 

Details:

CUCM IP is A.A.A.2/24

External IP is B.B.B.1

Phone IP is  C.C.C.2

As in this Figure 

So there no problem with conncetivity between Iphone and CUCM Server, Both an Ping each other as there is a port forwarding rule on Generic Router 2 to forward all traffic that's comming at IP B.B.B.1 to A.A.A.2

the problem is that CUCM does not accept registration using External IP B.B.B.1 

so is there any solution for this 

Note the This connectivity design can not be changed so I need a solution that make CUCM accept and recognize registration from external IP Phones

Thanks in advance

[Jonathan Schulenberg]

Woah. Do NOT expose CUCM to the public internet. Unless this is some sort of lab exercise you need to change the design.

The registration likely fails because SCCP/SIP embed IP addresses in the OSI Layer 7 payload. The NAT device would need to support application-layer inspection to rewrite both Layer 3 and 4 details. This rarely works reliably, even when using Cisco NAT devices.

The proper design for external phones is either to use Mobile and Remote Access through Expressway (7800 and 8800 series phones) or PhoneVPN with AnyConnect built in to the phone (7900, 8900/9900, 8800 series phones).