Connecting a PBX to a Router

Unanswered Question
Mar 27th, 2009
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Hello:


We have been tasked with migrating a Lucent 6000 PBX extender from its conventional WAN connection over a channelized voice-grade T1 to a Cisco 2821 ISR router.


Basically, what we are being tasked to do is migrate the T1 connection from the PBX extenders to the WAN interface on the Cisco routers (no biggie), and then connect a Cisco 3560 switch to the router's LAN interface, and then connect the PBX 6000 to the switch. SEE DIAGRAM.


My question involves how one goes about making the connection from the extender to the switch. The interfaces on the 6000 extender are 1) and Amphenol that faces some 66 blocks and eventually the phone sets; 2) a DB-25 WAN interface that connects to a CSU/DSU; and 3) an ethernet conenction that is supposedly used for management purposes only and "optionally" in a VoIP deployment.


So, it seems obvious that the ethernet interface will have to be the one facing the switch. But does it get configured as a trunk, a routed interface, or what?


I am envisioning the ethernet interface of the 6000 to be routed and placed on the same subnet with the router's LAN interface. And, of course, between the two of them is the 3560, with each one of its switchports configured for the same vlan - one switchport facing the 6000 and the other facing the routers LAN interface.


Does this make any sense at all????


Lastly, what is a PVDM module and what exactly gets plugged into it? How does it fit into this scheme of things that you see on the attached drawing?


Thank you to anyone who can help us!





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Laurent Aubert Fri, 03/27/2009 - 18:41
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  • Cisco Employee,

Hi,


What you want to do make sense at least to me :-)


your PBX becomes an IP PBX (it will now convert the voice received from the phone to ip packets) and its voice gateway is the 2821.


PVDM module are DSPs you added to your voice gateway and are used for analog/digital conversion of voice flows:


http://www.cisco.com/en/US/prod/collateral/modules/ps2641/product_data_sheet0900aecd8050918e_ps5854_Products_Data_Sheet.html


You will have to choose a signalling protocol for voice between the PBR and the router (H323, MGCP,..)


HTH


Laurent.

ex-engineer Fri, 03/27/2009 - 20:43
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"your PBX becomes an IP PBX (it will now convert the voice received from the phone to ip packets) and its voice gateway is the 2821."


So, are you saying that the voice traffic coming from the handsets and into the PBX Extender will be digitized (assuming it wasnt already), and then encapsulated into ethernet packets?


As a "gateway" what would be the exact function of the 2821? I was under the impression that the client just wants us to use the routers as an IP transport mechanism and operate only on the Network layer without doing any voice traffic manipulation/signalling. Is that a possibility or does that sound improbable?



"PVDM module are DSPs you added to your voice gateway and are used for analog/digital conversion of voice flows"


OK, so now Im more confused. :-) Isnt that voice traffic already digitized by the time it reaches the router? I would think that either the handsets or the PBX will digitize/packetize the voice traffic for encapsulation into an ethernet packet. No?



"You will have to choose a signalling protocol for voice between the PBR and the router (H323, MGCP,..)"


As for signalling, what exactly would be the interaction between the router and the PBX? Is the signalling taking place between those two endpoints?


Thank you very much for your help.

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