SRST with FXS

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Nov 12th, 2008
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Hello,


I have gateway with 4 FXS port. This ports are controlled by Cisco CallManager through MGCP.


I would do the following:

When link to CCM will fail FXS port should work with dial-peer on this Gateway.


With CCM all works fine, but then link fail FXS not work.

sh run in attach.


Thanks



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allan.thomas Wed, 11/12/2008 - 02:14
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In order for SRST to operate as expected, it has to be configured in the first instance, here is an example:-


call-manager-fallback

max-conferences 4 gain -6

transfer-system full-consult

timeouts interdigit 6

ip source-address x.x.x.x port 2000

max-ephones 36

max-dn 50


However, the main aspect which concerns me about your configuration is the fact that there are no outbound ports and pots dial-peers.


If the MGCP application controlled FXS ports unregister, it will be primarily because CallManager is down or the Gigabit interface goes down.


In either situation how will calls be forwarded from or to the gateway from the PSTN or from another IP Phone registered to another SRST gateway?


If you shut or disconnect the gigabit interface, I cannot see how your calls will be routed on-net or off-net even if registered to SRST?


You will require VoIP dial-peers in order to forward calls to and from these endpoints to other IP Phones on another gateway.


Please can you clarify your failover scenario so that we can understand your SRST requirements.


Hope this helps.

Allan.


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grisadovoy Wed, 11/12/2008 - 02:22
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Hello, thank you for your answer.


Commands, which you specify for SRST with IP Phone.


I have branch with 4 analog phone, which controled through MGCP. If link to CCM will fail analog phone сan call among themselves.


Thanks

allan.thomas Wed, 11/12/2008 - 02:54
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If that is the case, then you should only need to configure the call-manager-fallback commands as I mentioned earlier in order for this to work.


call-manager-fallback

ip source-address 172.23.5.41 port 2000



Rgds

Allan.



grisadovoy Wed, 11/12/2008 - 03:09
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I configure the following:


call-manager-fallback

max-conferences 8 gain -6

transfer-system full-consult

ip source-address 172.23.5.41 port 2000

max-ephones 5

max-dn 5


but in sh call-manager-fallback dial-peer


dial-peer voice 20001 pots

huntstop

progress_ind setup enable 3

port 50/0/1


dial-peer voice 20002 pots

huntstop

progress_ind setup enable 3

port 50/0/2


dial-peer voice 20003 pots

huntstop

progress_ind setup enable 3

port 50/0/3


dial-peer voice 20004 pots

huntstop

progress_ind setup enable 3

port 50/0/4


dial-peer voice 20005 pots

huntstop

progress_ind setup enable 3

port 50/0/5



SRST#


It is dial-peer for IP phone. Dial-peer 1 and 2 not persent. So in SRST mode this dial-peer not work.


Tahnks


allan.thomas Wed, 11/12/2008 - 03:39
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Hi Grigoriy,


You have already created the pots dial-peers for these analogue device, these dial-peers under call-manager-fallback are specifically for IP Phone, I would not expect the FXS to appear here.


I have just verified this on another MGCP gateway that has FXS ports, and this how it is configured. The initial issue that I had was that when in fall-back the FXS endpoint did not work primarily because I omitted the pots dial-peer with their respective destination patterns.


Allan.

grisadovoy Sun, 11/16/2008 - 15:42
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Hello, Allan


Thank you, for your investigation.


I have resolve the problem - problem was in IOS (i think it is Bug) - in 12.4.15T3 FXS with SRST not work. I have upgarde to 12.4.22T and all works fine. In attach final config.


Thanks


Best regards,

Grigoriy



allan.thomas Mon, 11/17/2008 - 00:51
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Hi Grigoriy, thanks for the update, glad that you were able resolve the problem with an IOS upgrade :)


I looked at the known issues for 12.4(15)T3 at the time, and although there were several documented bugs for the fxs issue, none exactly match your symptoms. Obviously there must have been in you case.


All the best.

Allan.

allan.thomas Wed, 11/12/2008 - 03:55
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Hi Grigoriy,


One aspect I forgot to mention, is that you should also try adding the following commands. (These cause MGCP to fall over and use H323 as the default application). :-


application

global

service alternate Default


However, what I have seen when doing debugging, is that when SRST is enabled, these commands appear in the running config anyway.


Take a look at this document for troubleshooting SRST and MGCP fall-back:-


http://www.cisco.com/en/US/tech/tk1077/technologies_tech_note09186a0080144630.shtml


Hope this helps.

Allan.

grisadovoy Wed, 11/12/2008 - 04:51
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Hi, Alan


I configure all that you say, but sh call-manager-fallback don`t show fxs voice-port and this dial-peer.


On your MGCP gateway is it show this?


In attach last config and show call-manager-fallback all


Thanks

grisadovoy Wed, 11/12/2008 - 04:58
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Hi, Alan


I configure all that you say, but sh call-manager-fallback don`t show fxs voice-port and this dial-peer.


On your MGCP gateway is it show this?


In attach last config and show call-manager-fallback all


Thanks



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allan.thomas Wed, 11/12/2008 - 05:03
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Hi Grigoriy,


Did you see my second to last post? Here I mentioned that the FXS dial-peers will not appear under the Call-Manager-Fallback.


The dial-peers associated with Call-Manager-Fallback will specifically be IP Phones, ATAs:-


dial-peer voice 20001 pots

destination-pattern 7601$

huntstop

progress_ind setup enable 3

port 50/0/1


dial-peer voice 20002 pots

destination-pattern 7602$

huntstop

progress_ind setup enable 3

port 50/0/2


There are already the MGCP controlled pots dial-peers, and also the pots dial-peer 1 and 2 which you have added. This should be sufficient.


Have tested the failover since adding the additional commands?

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