[cisco-voip] SRST Issue: Phones in Fallback Mode do have a different configuration than when registered to CUCM

[Hans Walter]

Hi List Members,


I do have a strange Problem in regards to SRST and i am running out of ideas
what is causing the issue.

I have installed a CUCM 7.1.3-2000 in my Lab Environment for Study purposes
with several IP Phones registered to it and a 2821 ISR Router with
c2800nm-ipvoicek9-mz.124-24.T.bin.

After reading up how SRST works and how it is configured, i started
immediately to test it out.

I have the following, SRST related, configuration on the 2811 Router.

 call-manager-fallback
 max-conferences 8 gain -6
 transfer-system full-consult
 limit-dn 7960 2
 ip source-address 172.16.7.254 port 2000
 max-ephones 58
 max-dn 192
 keepalive 20

The Feature itself is working like a charm. As soon as the connection to the
CUCM is gone, the IP Phones go in the Fallback Mode and register with the
SRST Gateway.

Now here is the strange thing i do not understand.

As soon as this happens the Phones have a complete different configuration
(e.g. the DN) as when they are registered to the CUCM.

As far as i understand, the IP Phones store the last configuration in Flash
memory, and when they register with the SRST Gateway, the Gateways retrieves
the configuration from the phones.

Now why do they have a complete different configuration? Shouldn't the
configuration, which is active when registered to the CUCM, stored as "last
configuration" ?

The configuration in SRST Mode is the configuration of a colleague of mine,
which had a lab before i got the telephones.

This behaviour does not occur on all IP Phones. 2 7960 work like i would it
have expected, they go in Fallback Mode and nothing changes.

All other IP Phones behave like mentioned above.

I have tried to do a Hardware Reset (plug the cable and put back in with the
# pushed), but this only solved the issue partially. Now when they go in
SRST Mode they have no configuration at all.

The 7960 have P00308010100 as App Load ID and Version 8.1(1.0). These 7960
are the ones which work without problems.

The 7962 have SCCP42.8-5-2SR1S and SCCP41.8-5-2SR1S and the 7911 has SCCP
11.8-5-2SR1S and all do not behave like expected.

So how can i fix this issue and what is causing it?

Sorry for the wall of text, i am quite new to the whole Voice World.

I hope a provided all information which are needed. If you need additional
information, don't hesitate.

Thanks in advance for your time and help

Cheers,
Chris
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