VOIP Infrastructure

Unanswered Question
Mar 25th, 2007


I'm studying the installation of VOIP infrastructure, not PABX, not analogic phones.

My interrogation relates the necessary material. I currently have a CISCO 1811 router, if I add a MCS-7815 server with the CISCO Call Manager software, that be sufficient to receive and send calls?

Thanks for your help.

I'm sorry for my english, i'm frenchies.

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Paolo Bevilacqua Sun, 03/25/2007 - 05:27

To work with the IP phones, you need an cisco switch, possibly with Power over ethernet, and CallManager.

Then you need a voice gateway (rotuer) to interface the PSTN. Best thing is ISDN BRI.

The 1811 does not do anything of the above.

Hope this helps, please are all useful posts!

cafecrm170 Sun, 03/25/2007 - 06:04

Thanks for your answer. I agree with the material which you quoted (Switch, Call Manager).

I don't understand the utility of the gateway. I thought that the gateway was useful if I had the IP phones and analogic phones, that is not my case.

I cannot use my WAN connections to forward my calls ?

Thank you.

Paolo Bevilacqua Sun, 03/25/2007 - 06:18

Yes you can use Internet for calls, using what is called an ITSP. However, for local and emergency calls, a local interface to the PSTN remains very useful. For this you use ISDN or, in second choice, analog FXO.

Now there is a feature in the router that does the basics of what callmanager does, however is not supported on the 18xx, the smaller router would be a 1751 / 1760 (these are EOS now) or 28xx. It is called CommunicationsManager Express (CME).

Hope this helps, if so please rate post!

cafecrm170 Sun, 03/25/2007 - 08:25

If I use a ITSP and only one ITSP without PSTN connection. Have I need a VOIP gateway?

My equipments would be then CISCO 1811 router, CISCO switch and CISCO Call Manager software.

I am sorry to insist on this point but this point remains imprecise.

Thnk you.

lpezj Sun, 03/25/2007 - 08:33


If you are planning to use a Voice 'IP' service provoder you can use your 1811 Cisco router to get a WAN connectivity with that IP provider.

But if you nees to get a PSTN connection (FXO, BRI or E1/T1) you need to adquire another router, 28XX or 38XX).

But with Cisco CallManager, MCS hardware to set uo the CallManager and you IP connection with your IP PSTN provider you will have a perfect IP PBX, but you will need to set up your connection to the IP PSTN provider as an H.323 gateway or H.323 or SIP provider.

Hope this helps,

Juan Luis

Paolo Bevilacqua Sun, 03/25/2007 - 09:11

Why imprecise? The matter of having location identifiable emergency call system is very simple.

Unless all users of the telephone system understand and accept that the system cannot provide emergency service,you must provide PSTN circuits, as a matter of common sense.

Failing to do so may have legal consequences in case an emergency arises and the agency cannot easiliy locate where are you.

This for commercial / semipublic use. Then if you are configuring for your home voip PBX, that is another matter.

cafecrm170 Sun, 03/25/2007 - 11:57


Can I use the VG224 Voice Gateway with my CISCO 1811 router ?

The CISCO 1811 router will be connected to my ISP Provider.

The VG224 Voice Gateway will be connected to PSTN.

Paolo Bevilacqua Sun, 03/25/2007 - 12:09

No, the VG224 is for analog phones, has ports called FXS. To connect to PSTN as I mentioned above, you need ISDN BRI or PRI preferably, or FXO ports and normal phone line.

Hope this helps, please rate all useful posts!

cafecrm170 Sun, 03/25/2007 - 12:20

Ok. The CISCO 1811 router have a integrated ISDN BRI. It's ok or not ?

I thank you for your patience and your help.

Paolo Bevilacqua Sun, 03/25/2007 - 12:28

Sorry, no. The BRI port on 1811 can be used for data only, not voice. In other words, the 1811 cannot be used as a voice gateway.

There is no problem in answering all questions here, but please remember to rate useful posts!

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