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Community Member

SRST fall back

I have an IPT site of ten branches and the Head Quarter (HQ).The callmanagers were located in the HQ while srst were configured on the branch routers. After the deployment all the branches were able to call the HQ. After few weeks of deployment, it was only three branches that could call HQ. During troubleshooting, I noticed that (1) the phones in one of the branches can call themselves but not any other phone outside the branch (fall back to srst but could not reconnect to the callmanager again). (2)the remainning could neither register with the callmanager nor the srst server. Please, can anybody be of help. Thank you.

Community Member

Re: SRST fall back

Hi hi,

Can I just verify what is the design for your setup?

Is your plan to have a centralised CCM in your HQ office and for the phones to register back to the CCM? In case of a outage, the phones would register to the SRST voice gateways?

Or is it supposed to use SRST in the branches all the time?

When you say after few weeks, only 3 branches can call HQ, this is when the phones are registered to CCM or in SRST mode?

Same question for when the phone in the branch can call themself, is this phone registered to CCM or in SRST mode?

Last point, when remaining phones can't register to SRST or CCM, can you check what is the network and device configuration on the phone? Is the IP address, TFTP correct? Does the CCM configuration shows the CallManager 1, 2 and SRST Hostname/IP Addresses?

Can you ping the phones?

All these would help to isolate where the problem lies.


Community Member

Re: SRST fall back

Thank u for d quick responce. The design is a centralised CCM in the HQ and all the phones to register back to the ccm.The branch offices phones should register to the srst voice gateway only in the event of outage.

After the deployment all the phone registered to the CCM in the HQ. After few weeks only three phones were able to register with the CCM.

The phones in the branch which can call only themselves are registered with the srst Voice gatway.My problem is that they can no longer register with the centralised CCM, and hence cannot call the HQ nor other branches.

Even the branches that can neither register with srst voice gatewy nor CCM were able to register with the CCM at the time the installations were done.

I will provide you with the answers for the configurations when I get to the site.

Community Member

Re: SRST fall back


I feel it is probably a network connectivity issue. There must be something causing the phones to not be able to reach the CCMs.

First check network connectivity, ping test, routing, Vlans.

If everything is okay, than is the CCM or phones behind any firewalls? Access-list?

Also check the network configurations on the IP phones, are they trying to reach the correct servers. If it is hostnames, check the DNS settings.


Community Member

Re: SRST fall back

Hi eug,

I will be at the site on monday. Thank u very much.


Community Member

Re: SRST fall back

Hi, I have a few suggestions.

First, was srst fallback tested prior to going into production?

Is the IOS consistent across all srst platforms and what type of IP phones do you have are they all the same? You might want to check to make sure the IOS on the srst supports the IP Phone your using at each branch ( assuming srst fallback wasnt tested ).

What protocol are you running on your gateways ? MGCP, H.323 ?

You might consider debugging packet and event error on MGCP or H.323 and also debug ccm-manager process events to see what is failing between the phone<>gateway<>callmanger.

Just a few suggestions, good luck.

Hall of Fame Super Red

Re: SRST fall back

Hi Eug-c and John,

5 Points each for your well thought out answers here!

Keep up the great work :)


Community Member

Re: SRST fall back

Hi Eug anh John,

I have a success staory. With the excellent and accurate suggestions, I vve been able to bring up all the branch phone exept one.

The problem were basically connectivity issues. in some of the branches the my client's ISP changed their network topology. Initially, the branches were linked direct to the HQ and our voice vlan network were advertised as such. Later, they linked the branches to their office (ISP) then from their office to the HQ. These were done without advertising our voice vlan network accordingly.

In one of the I noticed that the voice vlan does not exist in the vlan database. Probably, the vlan was deleted mistakenly by my client's support engineer. I simly created the vlan and the phones registered immediately.

The only branch that is not yet working needs my physical presence at the site since I cannot telnet the switch from the HQ. But with the beauitiful suggestion suggestion I'm sure I can resolve the problem.

Rob, thank u for appreciating the great work of Eug and John.

Remain blessed

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