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<div class="content wysiwyg-content">
Hi,<br />
<br />
I have the following hardware:<br />
<br />
1 x Cisco 2821 ISR router<br />
1 x Cisco c3750g T24<br />
3 x Cisco 7941G IP Phones<br />
<br />
I only need to make internal calls with the Cisco IP phones:<br />
<br />
- what Interfaces/other components do I need?<br />
- What software do I need (and more importantly, will I have to pay for it)?<br />
- Are there any step-by-step guides to configure this?
</div>
</div>


Hi,

I have the following hardware:

1 x Cisco 2821 ISR router
1 x Cisco c3750g T24
3 x Cisco 7941G IP Phones

I only need to make internal calls with the Cisco IP phones:

- what Interfaces/other components do I need?
- What software do I need (and more importantly, will I have to pay for it)?
- Are there any step-by-step guides to configure this?

Components Needed to Set-up an Internal Cisco VoIP Network

Voice over IP (VoIP) is a methodology and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. Other terms commonly associated with VoIP are IP telephony, Internet telephony, broadband telephony, and broadband phone service. The term specifically refers to the provisioning of communications services (voice, fax, SMS, voice-messaging) over the public Internet, rather than via the public switched telephone network (PSTN).  Examples of the VoIP protocols are H.323, Media Gateway Control Protocol (MGCP), Session Initiation Protocol (SIP), H.248 (also known as Media Gateway Control (Megaco)), Real-time Transport Protocol (RTP), Real-time Transport Control Protocol (RTCP), Secure Real-time Transport Protocol (SRTP), Session Description Protocol (SDP), and Inter-Asterisk eXchange (IAX).

Voice Over IP

IP telephony (Internet Protocol telephony) is a general term for the technologies that use the Internet Protocol's packet-switched connections to exchange voice, fax, and other forms of information that have traditionally been carried over the dedicated circuit-switched connections of the public switched telephone network (PSTN). Using the Internet, calls travel as packets of data on shared lines, avoiding the tolls of the PSTN. The challenge in IP telephony is to deliver the voice, fax, or video packets in a dependable flow to the user.

IP Telephony

Network design and methodology, also known as network architecture, is the design of a communication network. It is a framework for the specification of a network's physical components and their functional organization and configuration, its operational principles and procedures, as well as data formats used in its operation. In telecommunication, the specification of a network architecture may also include a detailed description of products and services delivered via a communications network, as well as detailed rate and billing structures under which services are compensated.