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Infrastructure Design for IP-Telephony

Level 1
Level 1


      I would like to implement IP-Telephony using Cisco UC-520 router. In our Existing Infrastructure we have ISA server 2006 as Gateway and Router also as firewall between the Internet and the LAN

     Now I would like to place UC-500 between Internet and the ISA server. Since I do not have POE switches on my existing LAN. I planned to directly connect the IP phones to UC-500(This will bypass going thriugh ISA). This would work fine. But my problem is, We are going to use the IP Communicators in our LAN systems which has to pass through the ISA server and reach CME. can anybody give me idea about making this happen?

               Or suggest me if there is any better design for this... Thanks

6 Replies 6


You're asking about what to allow through the ISA server?

The IP communicators will use Skinny TCP 2000 to register with the CME.

You should also allow RTP/RTCP for the voice streams.

If you can provide a diagram or more details we can help you further.


Please look at the diagram attached. LAN has a DHCP server whilch is handing out IPs to LAN systems. On few of the LAN Systems Cisco IP Communicator is installed. Also look at the IP addressing. IP phones anyway get the IPs from the DHCP of UC-500 along with the TFTP server address which is running inside UC-500

In this my only concern is how to make IP communicators work. Suggest me on this.


The IP communicator will use the IP of the computer where it reside.

You can configure on the IP communicator the TFTP server IP address so that it can download the configuration.

The IP communicators should register and work just like any other IP phone (even though there are in a different IP subnet).


That gives me clear understanding now. Thank you veymuch for the help. One last question will end my confusion on this Voice implementaion.

I have created two vlans on UC-500 one for DATA and other for VOICE. I have connected the IP phone to the switch on the router and PC connected to the switchport on the IP phone. In this case the  IP phone created mini trunk and passes the DATA traffic to PC so both traffics are isolated for QOS

Where as in the case of IP communicator how this isolation will be maintained for QOS. how should I plan my VLAN configuration


The QoS for the IP phones can be based on VLANs (since they are on a separate VLAN).

The QoS for the IP communicators cannot be based on VLAN (since they share the VLAN for data traffic on the computer they reside).

In this case, you can configure CoS on the switch to mark the voice packets and differentiate the voice payload from the data payload.


Thanks for all the help. Will let u know how it works.

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