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New Member

Setting up VoIP without using a PBX


I am getting a proposal together to configure 2 LANS for VoIP without using PBXs. I am hoping that I can get some feedback or guidance on an entry level solution as the company is small (about 10 users at both premises).

At each LAN I am hoping to use Cisco IP Phones, connected (by Fast Ethernet) to a QoS capable switch (that may or may not have power for the phones built in), that in turn connects to a Cisco 1751-V. Both sites will be connected via the routers using a 512K leased line to send both the voice and data traffic.

I am also hoping to setup Cisco CallManager 3.x to handle the call routing on a windows platform (probably Windows 2000).

VoIP is completely new to me and am finding it difficult to get through the vast amount of information available on the Cisco website, so I look forward to any feedback on the potential solution.

Cisco Employee

Re: Setting up VoIP without using a PBX

Sounds like you have a plan. I usually recommend at least 2 CallManager servers for redundancy, but that's up to you (many folks buy pbxs without redundancy or key systems). If you have a single server I'd recommend redundancy in the box, so a MCS-7835 (Compaq DL380) or IBM Netserver x342. Note that these MUST be purchased from Cisco or match specifications posted or the software will not install - there are hardware checks. See:

The OS WILL be W2K server if you're using CallManager, as that's the only thing it's certified on and it is a part of the automated installation (install CDs image the drives and install Win2k server, SQL 7.0, LDAP directory and CallManager, All licensing included).

The 1751 supports SRST (Survivable Remote Site Telephony) for 24 phones on IP/VOICE/PLUS and above images so if the CallManager is at one location and the WAN goes down, the phones at the other location get dial tone, their extension numbers, speed dials, transfer, DID, DOD, etc. Make sure you purchase the SRST license for the remote router, and check the memory requirements.

With this sizing you may also look at ITS - IOS Telephony Services. It's basic telephony services (aka key system-like features) on IOS (the router). No CallManager servers are involved. It involves a subset of the CallManager features, but may be ok for the implementation you're planning. If you want the full feature set then go with CallManager, and you can roll out to additional sites as needed.

As far as hardware, you can use the 3524-PWR-XL-EN 10/100 switch for data and inline power to the phones. This automatically provides QoS based on CoS (802.1p). You can also look at the new 16 port etherswitch module for the 2600/3600/3700. I don't know how this will price out for you but would fit your application well as you put the WIC into the built-in slot on the 2600 and your 10/100 switch-ports into the NM slot. The etherswitch mod does support inline power for the phones as well.

Hope this helps.

New Member

Re: Setting up VoIP without using a PBX

Thanks for all the information in the reply Doweiner, it is nice to know that I'm going in the right direction and to get back such detail.

I just have some more questions, if I choose not to use a PBX in the topology how can the customer receive calls from outside this topology (non VoIP or POTS) ?

Also, I am having difficulty finding information on the IOS Telephony Services, can you or someone suggest/advise me of a URL to look at?

Thanks again for all the help.


Cisco Employee

Re: Setting up VoIP without using a PBX


You'll use a gateway to go from VoIP to PSTN. The gateway is like the "trunk card" in a PBX., except your choices are numerous and you put it wherever you want. Some ISPs have started providing gateways, so you might be able to avoid this and go IP directly to the ISP providing Internet access and they gateway to the PSTN for you. If you provide it yourself (most common at thispoint in time), the gateway you choose for this configuration will really depend on how many trunks and what type of trunks (analog or fractional T1). You'll connect directly to the Local Exchange Company as you would with a PBX or key system. With the number of users you have you could, depending on calling patterns, use a VG200 with an NM-2V with 2 VIC-2FXO (4 trunks total), or use a 2610XM with NM-HDA with EM-HDAs (4 ports each, max 2 per NM-HDA). Of course the 2600 that acted as a gateway could also be your data router at that location, as well as the "pbx" if using ITS.

If you go to and search on "IOS Telephony Services" you should get a bunch of hits. Naturally, information is more detailed if you have a login.


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