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Basic SRST Configuration (SCCP only)

Cisco SRST Configuration

Survivable Remote Site Telephony (SRST) – It is a call processing backup mechanism that allows Cisco IP phones to register to a Cisco router locally during a WAN Failure. Let’s say you are connected to your Headquarter Site A remotely via Site B using WAN. In case, the WAN links goes down, IP Phones at site B should register to the local Site B router to avoid any outages. In this case, you VoIP calls inter-clusters will not work as the WAN link is down but however calls made to the local site will work as the phones will be registered to the local router. As the Phone will register to the local site, the mode is called as SRST Fallback Mode.
Let’s do the basic configuration.
———————————————————-CUCM Configuration———————————————————-
Step 1>Configuring the SRST Reference

Go to System > SRST > Add a New SRST Reference
Name – Site B SRST
Port – 2000
IP Address : – X.X.X.X (IP Address of the Site B Router)
Click on Save

Step 2> Adding the SRST Reference in the Device Pool of the Site B Phones.

Go to System > Device Pool > Select Appropriate Device Pool which is assigned to the Phones at Site B
SRST Reference* > Select the SRST Reference created above
Click on Save, Apply and Reset (Ensure that you reset the DP after business hours)

———————————————————-SRST Configuration on Router———————————————————-
To Enable SRST on the Site B Router, you need to configure the below.

call-manager-fallback
ip source-address X.X.X.X port 2000    ——> This is the IP Address of the Site B Router
max-ephones 5
max-dn 5
system message primary SRST FALLBACK

Note:- The above configuration will only make your IP Phone fall into SRST mode. To make/receive PSTN calls, you need to configure all relevant configuration like E1/T1, dial-peers, DSPs/Transcoders etc.
During a WAN Failure, your Phone will fallback into SRST mode as shown below.

R1#
*Mar  1 01:09:37.091: %IPPHONE-6-REGISTER_NEW: ephone-1:SEP00255649DF28 IP:10.1.1.3 Socket:2 DeviceType:Phone                                                           has registered.
R1#
R1#
R1#sh ephone regi
R1#sh ephone registered
ephone-1 Mac:0025.5649.DF28 TCP socket:[2] activeLine:0 REGISTERED in SCCP ver 12 and Server in ver 5
mediaActive:0 offhook:0 ringing:0 reset:0 reset_sent:0 paging 0 debug:0 caps:6
IP:10.1.1.3 3405 Telecaster 7960  keepalive 13 max_line 6
button 1: dn 1  number 81011002  CM Fallback CH1   IDLE
Basic-SRST-Fallback-Softphone

Published by Team UC Collabing

One thought on “Basic SRST Configuration (SCCP only)”

  1. Claudio says:

    Good post !
    I think you should publish an articule about SIP SRST and its requeriments on ISR platforms.

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Electrical Engineer CCNA Collaboration CCNA Voice CCNA R&S. I'm Electrical Engineer and I work like Support Engineer for a Telephony Service Provider Company. Before that I had position like Pre-Sale Engineer about small and medium multivendor telephony solutions. I have 5 years of experience working in Telephony Multivendor Projects. I am also 3 years of experience working in Support and implementation about Cisco Collaboration platforms: UCS server, UCM, Cisco Unity, Presence Server, Jabber, Gateway. Support Community is most useful in finding design, implementation and support tricks and shortcuts that greatly help me in my daily activities. If you need to contact me, please you can writte me.

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CCNA Routing and Switching
Am a technology enthusiast. I work in network support providing support with implementation, maintaining and precisely troubleshooting the infra.
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