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VoIp Gateway and its Public IP

Hi everybody.

  First at all, I am relatively new in this area so I hope you will understand if something in my question does not make sense.

  Now, my question is this, in a company there is a CISCO voip gateway which model number is: IAD2431-16FXS. Do I need to register the public IP address assigned to it with some company for the people to call us through the internet? If the answer is yes, then I would understand that I need to change it if I move the gateway to antoher IP. I hope someone to help me.

Thanks in advance for your answers.


Cisco Employee

Re: VoIp Gateway and its Public IP

I'm not completely sure what you have in mind, but that GW is for analog connections (phone/fax machine)


Analog FXS voice ports over RJ-21 connector

One 8-line or 16-line analog or 24-line FXS interface (loop-start or ground-start) for connection to analog phones, key systems, or PBXs.



If this helps, please rate



if this helps, please rate

Re: VoIp Gateway and its Public IP


You're new - no biggie, that's what the forums are for.  To answer your question, you do not need to register the public IP address of the gateway in order for it to receive calls.  As Java said, this is an analog gateway so there is no use case for doing so.  In fact, this would probably never be necessary.

On to other things.  I would strongly recommend against having public IP addresses assigned to your voice infrastructure unless you are well protected from unauthorized external access.  There are some that would argue public vs. private addressing doesn't really matter.  I am of the latter opinion unless there is some special requirement or use case that must be accomodated in this fashion.  In either case, you still need to be protected from external attack (in general).

As for when the gateway IP may be important, that comes into play more internally - i.e., for internal communication between the voice infrastructure devices and the phones.  As for external entities, this might come into play if you were doing some sort of inter-company SIP configuration; however, even then most things would flow through a proxy server and, in the end - callers would still dial your end users by number (i.e., they are blind to where the call goes other than knowing the person answers on the other end).



New Member

Re: VoIp Gateway and its Public IP

Thank you very much for your answers.

  I am going to explain better what I pretend to do. In that company, they want me to change the gateway along with the pbx connected to it to another location with another public IP. The gateway is behind an ADSL modem/router. So, what I want to know is if all what I have to do is just to take them to another place and connect the gateway to the ADSL router (Performing the changes to the private IP within the modem/router in order to make the gateway to work with it). Thank you very much!!!



Re: VoIp Gateway and its Public IP

Hmm..So what you have provdided I guess your setup is something like this?

Some Voip internet service (ATT, Timewarner, Vonage, etc.)-->ADSL modem-->Cisco gateway--FXS-->PBX

If that is the case, then I don't believe you would need to change anything on the gateway side as long as the Public IP is the same.

In my experience with those types of services will map the a static IP to the mac of the modem. We would probably need to see the config from

the gateway to tell you for sure, but with the info you have provided I believe you would probably be able to move without having to reconfigure

the gateway.

Re: VoIp Gateway and its Public IP

Yeah, I would agree on all points.

Sent from my iPhone

On Feb 19, 2010, at 5:47 PM, jaschulz

New Member

Re: VoIp Gateway and its Public IP

Thank you very much to all of you for the answers. :-)

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