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Ehsan M.
Beginner

How to register IP Phones with Callmanager 4.1 over the internet (Remote office scenario)

We have a remote office that would like to register their IP Phones (very few phones by the way) with our Callmager 4.1 at the head office in order to avoid long distance charges. I'm sure this is a very common scenario and I’m just looking for some advises on basically how to do it and also what are the hardware requirements beside the phones that should be purchased for the remote office as they currently have no router, switch (PoE switches) or Callmanager application in place (and preferably don’t want to invest on this equipments as much as possible). Here is a summary of the configuration at the main office:

  • 1 x Cisco Callmanager 4.1
  • 1 x Cisco 2821 Router acting as a voice gateway through a T1 connection to Telco (PSTN)
  • about 20 x Cisco IP Phones 7940 Series
  • 2 x Cisco 3560 PoE switches

On the other end at the remote office we'd like to be able to register their brand new ip phones (7940 series the same as head office) with our Callmanager at the head quarter and also route all their VoIP traffic through our gateway the same as they'd be at the head office.

Please advise with some recommendations as this is the first time I'm trying to accomplish such a task!

Thanks,

1 ACCEPTED SOLUTION

Accepted Solutions
abdul ilyas
Beginner

Hardware:

1. You may have it already, if not need to have a router at remote office to establish IP connectivity (site-site VPN).

2. Need Layer2 PoE switch to power up the phones and provide connectivity to the network.

    Select the Switch model best suitable to you depending upon the number of users (or IP Phones at remote office).

Configuration:

1. Configure DHCP service on local router at remote office. Phones will get IP-address as well as CallManager address as option 150 ip parameter from DHCP configured on the router and get registered with CallManager located at HQ office.

2. Configure new device pool and other parameters on the CallManage for remote office.Choose right codecs and pay special attention to bandwidth requirements depending upon the number of expected simultaneous calls between the offices.

3. Trivial things like assigning extension numbers and related settings.

4. Implement and configure QoS on the remote office if you are planning to run data as well.

Optional:

1. For redundancy, during WAN network outage. Configure SRST on local route on remote office to continue support basic telephony during WAN outage.

2. May need Voice modules on the router, if you are planning to provide local pstn connectivity at remote office. You'll need to configure and implement dial-plan carefully on the CallManager.

View solution in original post

4 REPLIES 4
Brandon Buffin
Advisor

Is there existing IP connectivity from the remote office to the HQ? If so, you will simply need DHCP at the remote location to hand out option 150 to the phones. Option 150 is used for TFTP and should be the IP address of your CCM TFTP server.

Hope this helps.

Brandon

Hi Brandon,

Thanks for the quick reply!

No. Unfortunately at this time there is no direct ip connectivity between HQ and remote office... I understand VPN might sounds a great idea here but there is no VPN-enabled router on the other site too (although on the main site our 2821 router should take care of the job quiet well!). Beside VPN, are there any other ways to get the phones registered with the callmanager\TFTP server at HQ over internet?

Thanks,

There are 3 options that I can think of:

1. Open the necessary ports so that the phones can connect to the CCM directly over the internet (Not recommended).

2. Use the ASA Phone Proxy functionality. This obviously requires that you have an ASA. See the following link.

     http://www.cisco.com/en/US/solutions/collateral/ns340/ns394/ns165/ns391/white_paper_c11-493584.html

3. Some newer phones/firmware (7942G, 7945G, 7962G, 7965G, and 7975G) have a built-in VPN client to allow remote connectivity. See the following link.

     http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7975G_7971g-ge_7970g_7965g_7945g/8_0/english/administration/guide/7970set.html#wp1271763

Hope this helps.

Brandon

abdul ilyas
Beginner

Hardware:

1. You may have it already, if not need to have a router at remote office to establish IP connectivity (site-site VPN).

2. Need Layer2 PoE switch to power up the phones and provide connectivity to the network.

    Select the Switch model best suitable to you depending upon the number of users (or IP Phones at remote office).

Configuration:

1. Configure DHCP service on local router at remote office. Phones will get IP-address as well as CallManager address as option 150 ip parameter from DHCP configured on the router and get registered with CallManager located at HQ office.

2. Configure new device pool and other parameters on the CallManage for remote office.Choose right codecs and pay special attention to bandwidth requirements depending upon the number of expected simultaneous calls between the offices.

3. Trivial things like assigning extension numbers and related settings.

4. Implement and configure QoS on the remote office if you are planning to run data as well.

Optional:

1. For redundancy, during WAN network outage. Configure SRST on local route on remote office to continue support basic telephony during WAN outage.

2. May need Voice modules on the router, if you are planning to provide local pstn connectivity at remote office. You'll need to configure and implement dial-plan carefully on the CallManager.

View solution in original post

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