CME as SRST

[miket]

Can some please clarify for me the difference between CME as SRST or callmanager fallback. They both appear to work the same way.  Documents are not very clear.

Thanks

[Adarsh Chauhan]

Hi Miket,

let me try to break it down for you. 

Though both get the job done, while SRST provides a large scalable fallback support, CME as SRST provides less scalability but with more features.

SRST:

Features supported:

1. During Cisco Unified CM fallback, Cisco Unified SRST considers the Cisco VG248 to be a group of Cisco Unified IP phones. Cisco Unified SRST counts each of the 48 ports on the Cisco VG248 as a separate Cisco Unified IP phone.
2. Maximum number of phones supported for fallback.

CME as SRST:

When Cisco Unified SRST functionality is provided by Cisco Unified CME, provisioning of phones is automatic and most Cisco Unified CME features are available to the phones during periods of fallback, including hunt-groups, call park and access to Cisco Unity voice messaging services using SCCP protocol. The benefit is that Cisco Unified Communications Manager users will gain access to more features during fallback without any additional licensing costs.

An advantage of SRST fallback support using Cisco Unified CME is that you can choose to prebuild a Cisco Unified CME configuration that contains a number of extensions (ephone-dns) with additional features that you want them to have for some or all of your extensions. The configurations will contain ephone-dn configurations but will not identify which phones (which MAC addresses) will be associated with which ephone-dns (extension numbers).

These features are not supported with SRST fallback support using Cisco Unified CME.

1. More than 240 phones during fallback service
2. Cisco VG 248 Analog Phone Gateway support
3. Secure voice fallback during SRST fallback service
4. Simple, one-time configuration for SRST fallback service

Please rate and mark correct if helpful

Regards,

Adarsh Chauhan