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New Member

One central CCME, multiple locations with phones

Hi everyone,

Is it possible to have one central CCME, but have 5-6 phones in remote locations?

The majority of my users are in one location, however I have a few users in different buildings across the city. Can a 7940 phone on one subnet in building X connect to the CCME in building Y across the WAN?

Thanks.

-- Dominique

7 REPLIES
Silver

Re: One central CCME, multiple locations with phones

This configuration is not supported. That said, if they VPN in it should work.

Steve

New Member

Re: One central CCME, multiple locations with phones

Thanks for your reply Steve.

Would using the full Call Manager allow this or do I still need some call routing functionality, SRST, etc..

You mentioned VPN, if I built a vpn tunnel between the Central Office and the Remote Location. How would having a vpn system be different then actual different private subnets.

Thanks.

-- Dominique

Silver

Re: One central CCME, multiple locations with phones

CallManager would be supported. The real issue is TAC support, multi-site CME is not supported. It is meant to replace a small key-system at a branch office.

SRST would be needed if you wanted the site to have a backup to the CallManager system, for example if the WAN link dropped so the remote site still had telephony service. This is the prefered design although not required.

Steve

New Member

Re: One central CCME, multiple locations with phones

According to current information from Cisco, remote phones on a Unified CME are supported.

This feature was introduced with in IOS 12.4(4)XC, the configuration-details can be found here http://www.cisco.com/univercd/cc/td/doc/product/voice/its/cme40/cmesa/cmesappn.htm#wp1056386

Regards

Markus

New Member

Re: One central CCME, multiple locations with phones

I've done this on a test network, but I had to manually configure the remote phone to tell it the IP address of the CCME router. The remote phone was in a different IP network than the CCME router, across several WAN links. It worked fine, but like I said, I was only testing it out. As others have pointed out, it's not a supported configuration, and if you don't/can't configure QoS on the WAN link(s) and remote LAN, your voice quality is going to suffer whenever network utilization is up.

New Member

Re: One central CCME, multiple locations with phones

Of course this is possible. I have CCME at main office and I am running phones (7940's)off of it via site to site VPN. WAN setting would be the same. All that is really required is that the ip phone know where CCME router is located. That means set up a DHCP pool with "option 150" setting. On my remote side I have a PIX firewall with DHCP enabled and this command "dhcpd option 150 ip 192.168.14.1" where 14.1 is my CCME router. The local network for my remote office is 192.168.13.1 the 7940 phone gets an IP address from the DHCP pool on the 192.168.13.X network and registers with 192.168.14.1 router. it is that simple.

New Member

Re: One central CCME, multiple locations with phones

Of course, it's "that simple".

Until a few weeks ago, this setup was not supported by Cisco. Fine if it works, if not don't blame it to Cisco. You could only use G.711 in this setup, "worst case" you would need around 85 kbit/s per call. In the new IOS, you can configure remote phones to use G.729, reducing the necessary bandwidth to 25 kbit/s or even below.

Regards

Markus

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