Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

dhcp and srst

customer has ccm bus edition, 6.1.2. have a local 2851 router/gateway running srst. ccm is dhcp server for phones. I've tested the srst function, but today the server malfunctioned and phones did not go into srst mode. instead the phone display said " ip address released".

the server remained connected but could not be pinged.

any idea why phones didn't go into srst?

I arrived on site after the server motherbd was replaced and when server was shutdown, phones went into srst mode.


Hall of Fame Super Silver

Re: dhcp and srst

The phones did not register with SRST becuase they lost the IP address lease. How long is the DHCP lease set to on the server? If it's very short that would cause the problem.

Honestly I would recommand provisioning the router to provide DHCP services to the phones to avoid situations like this.



New Member

Re: dhcp and srst


It was my understanding that a phone would not release an address if it could not contact the dhcp server. is that not right?

What is recommendation for lease time?

Agree with putting dhcp on the router.



Hall of Fame Super Silver

Re: dhcp and srst

Correct, the way DHCP works is the device renegotiates the lease half way through the lease time, so if your lease time is 30 days the device will attempt to renew the IP after 15 days.

Anything from 7 to 30 days.


Re: dhcp and srst

Further to the good information by Chris, another reason to be aware of is that there maybe still situations where the IP Phones were still able to communicate with the primary CallManager.

In this situation the IP Phones would still be receiving keepalives from the Publisher, and only in the event that it missed these keepalives would the IP phone re-register to the gateway.

Essentially the server did not experience a complete failure, and as soon as the server was shutdown the IP Phone would longer receive the keepalives and after approx. 90 seconds the phone would re-register.