SRST registration process

[banst8801]

Hello folks,

I know that regular ip phone registration process is as follow:

 1.-The phone has received PoE from the switch.

 2.-The phone has received VLAN info.

 3.-The phone has received IP info from DHCP server.

 4.-The phone has downloaded its configuration file from TFTP server.

IP phone registration process is the same for SRST?

Regards, 

[Manish Gogna]

Hi,

When Cisco Unified IP phones lose contact with primary, secondary, and tertiary Cisco Unified CM, they must establish a connection to a local Cisco Unified SRST router to sustain the call-processing capability necessary to place and receive calls. The Cisco Unified IP phone retains the IP address of the local Cisco Unified SRST router as a default router in the Network Configuration area of the Settings menu.

The system automatically detects a failure and uses Simple Network Auto Provisioning (SNAP) technology to autoconfigure the branch office router to provide call processing for Cisco Unified IP phones that are registered with the router.

More details in the following guide

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cusrst/admin/sccp_sip_srst/configuration/guide/SCCP_and_SIP_SRST_Admin_Guide.pdf

Manish

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[banst8801]

Thank you Manish!

I have one more question.

is SNAP used for SCCP phones only?

[Manish Gogna]

That is correct, for checking how SIP SRST works you can check the "Cisco Unified SIP SRST" section of the following link

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cusrst/admin/sccp_sip_srst/configuration/guide/SCCP_and_SIP_SRST_Admin_Guide/srst_overview.html#10056

Manish

[Vladyslav.Shvedenko]

Hello,

Yes, SRST is kinda Cisco Communication Manager Express (CUCME) thus all the process is going to be the same : you just have another benefit to route your call flows via alternative PSTN/SIP connected ITSP in case of WAN or main CUCM disconnection appeared.

As in case of CME, SRST will also provide a possibility to configure local TFTP for your ip phones firmware and configurations' file as well, as general local registration (SCCP/SIP) on your router.

[Jaime Valencia]

That is not quite right, you only get a local configuration files and enhanced call routing capabilities if you enable CME-as-SRST.

Regular SRST provides basic fallback functionality, but the phones use the current DN they have to simply register to the SRST router.

[banst8801]

So, if a branch phone lose connection to its primary CUCM, and the phone is running firmware version 9.2 for example. when the phone get register to SRST router, which firmware version will use the phone if the SRST router can provide 9.3 firmware version?