SRST vs CME for temporary use?

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May 3rd, 2010
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We have a small branch office location which will soon go live with about a dozen people. They will be connected to our main site by a less then perfect VPN until some data circuits go in a couple of months from now. They'll have a Cisco 3845 with a PRI when the office opens.

Any thoughts on whether it's easier to use a small CME license and run a stand alone phone system, or easier to let things register remotely then run SRST?  Either way our voice needs are largely local and simple, and once the data circuits go in we can register everything with CM in our main site.

We've done brief SRST setups like this before, but never for more then a couple of days.  The hard part is usually the long wait for phones to load before we cut them off from CM.

Any comments from people who play with SRST / CME more then I do (which is probably everyone) are appreciated.



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Overall Rating: 4.5 (4 ratings)
paolo bevilacqua Mon, 05/03/2010 - 13:08
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Try SRST in CME mode and enjoy the best of both.

David Hailey Mon, 05/03/2010 - 13:13
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Personally, if it's temporary - I'd say this is a case of "6 in one hand, half dozen in other".

mark.doyle Mon, 05/03/2010 - 13:56
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Ah!  Thanks.

I didn't realize that was even an option and I'm reading about it now.  Am I right that this wouldn't require a FL-CCME-SMALL feature license?


Giuseppe Larosa Mon, 05/03/2010 - 13:29
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Hello Mark,

>> and once the data circuits go in we can register everything with CM in  our main site.

I may be wrong but in order to use SRST the phones have to have been registred to CUCM on central site, because in SRST mode the VGW receives the phone configuration via SNAP.

if phones are not able to register with CM, they cannot receive their configuration and SRST will not be able to handle them.

if so standalone CME is your only option.

But I guess you mean the VPN may exhibit intermittent IP connectivity to central site and so SRST can work.

CME in SRST mode would allow you to have more features for less phones (up to 240 on a C3845)

Hope to help


paolo bevilacqua Mon, 05/03/2010 - 13:44
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Well that's the point of having a-priori config on the local telephony device.

Suppose an event zaps circuit and router at a branch, then a replacement router comes blank from stock, before the circuit is re-established.

You will want your device to be working regardless of downloaded config, a fundamental issue that MGCP and SNAP cannot address.

You may like better CME anyway then and run it as a trunk.

mark.doyle Mon, 05/03/2010 - 13:54
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You are coorect, we would bring the router and phones up across the VPN long enough to register, then break the connection and go to SRST.  It's not always pretty, but it generally works well enough to get the loads.



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