primary SIP and backup ISDN PRI line

Answered Question
Apr 15th, 2009
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Hello dear friends,


i have one question on the subject described up. On 2821 router I have SIP to SIP connection to my ISP and we are planning to add on this router new ISDN card that will come active when the SIP connection goes down.


Can you please point me in the right way, give me an example how to do that. Is it possible to configure this in CUCM or has to be configured directly on the router?


So the question is how to make backup from SIP as primary connection to ISDN PRI(TDM) ?


Thank you realy for you help and time!



Sebastjan Stucl

IBM Slovenia

[email protected]

Correct Answer by iventurini about 7 years 11 months ago

If you are using MGCP you should see the different endpoints. I am not sure but you should see the sip to sip, and the pri interface.

So you can put each into a distintc route group.

Then you could add a new route list. In route list you can add several route groups, and give them an order (so sip to sip should be first and pri at last).


Then you can use this route list in your route patterns for outgoing calls.


Regards,


Ignacio



Correct Answer by iventurini about 7 years 11 months ago

To give specific dial peers in the pool a preference over other dial peers, you can configure the preference order for each dial peer by using the preference command. The router attempts to place a call to the dial peer with the highest preference. The configuration example given for Router B shows that all dial peers have the same destination pattern, but different preference orders.

Here is some extract form "Dial Peer Configuration on Voice Gateway Routers"

http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/dial_peer/dp_confg.html :

"The lower the preference number, the higher the priority. The highest priority is given to the dial peer with preference order 0. If the same preference is defined in multiple dial peers with the same destination pattern, a dial peer is selected randomly.


I dont know if the router is smart enought to forward all calls on other backup if the primary line goes down.

I have configured dial-peer preference between two ISDN E1 lines and when a one ISDN line response "destination unreacheable" the router try in the second E1 line.


I was searching when preference takes effect but i didnt find much information.


Could please send the dial peer configuration?


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iventurini Thu, 04/16/2009 - 04:44
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I am not sure but you could use a route list in CUCM for outgoing calls.


Another option is to use the "preference" option in your dial-peers directly in the router.


Hope that helps

sebastjan.stucl Thu, 04/16/2009 - 05:53
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Yes mr. Iventurini this was very helpful, but I have to add one more question to this.


Do you have to configure anything on CUCM?

Or it is enought to add "preference" on router?


Router is smart enought to forward all calls on other backup if the primary line goes down?


What is the difference if you use SIP as backup or ISDN PRI for backup?


I'm using SRST and MGCP on that router, and I have one preference already at SRST. Is this the same scenario? Regarding on this SIP should have preference 0 , ISDN preferene 1 and SRST preference 2?


Thank you for your time and answer..



Correct Answer
iventurini Thu, 04/16/2009 - 06:38
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To give specific dial peers in the pool a preference over other dial peers, you can configure the preference order for each dial peer by using the preference command. The router attempts to place a call to the dial peer with the highest preference. The configuration example given for Router B shows that all dial peers have the same destination pattern, but different preference orders.

Here is some extract form "Dial Peer Configuration on Voice Gateway Routers"

http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/dial_peer/dp_confg.html :

"The lower the preference number, the higher the priority. The highest priority is given to the dial peer with preference order 0. If the same preference is defined in multiple dial peers with the same destination pattern, a dial peer is selected randomly.


I dont know if the router is smart enought to forward all calls on other backup if the primary line goes down.

I have configured dial-peer preference between two ISDN E1 lines and when a one ISDN line response "destination unreacheable" the router try in the second E1 line.


I was searching when preference takes effect but i didnt find much information.


Could please send the dial peer configuration?


sebastjan.stucl Thu, 04/16/2009 - 07:11
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Great iventurini, you are making my life easier :-)


Hmm, I will post configuration tomorrow when I'll be at customer side.


When you configured dial-peer preference between two ISDN E1 lines, did you have to change anything on CUCM? Or configuration on router was enought?


Thank you iventurini!

iventurini Thu, 04/16/2009 - 13:01
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If your gateway is in H323 (not MGCP) then you have to do nothing in CUCM.


If your gateway is in MGCP the preference option will aplly only in SRST mode, and you'll have to configure route groups and route lists in adition.


sebastjan.stucl Fri, 04/17/2009 - 00:33
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Iventurini as I've said up I'm using MGCP combined with SRST mode. This means that dial-peer is here not an option?


Can you maybe tell me or give me an example how to configure this on CUCM (MGCP).

And how does CUCM knows when the connection to primary link SIP-SIP is unreachable?


Thank you again mr. Iventurini

Correct Answer
iventurini Fri, 04/17/2009 - 03:26
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If you are using MGCP you should see the different endpoints. I am not sure but you should see the sip to sip, and the pri interface.

So you can put each into a distintc route group.

Then you could add a new route list. In route list you can add several route groups, and give them an order (so sip to sip should be first and pri at last).


Then you can use this route list in your route patterns for outgoing calls.


Regards,


Ignacio



DOMJAHN DAVID Thu, 03/04/2010 - 07:59
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That's interesting!

Is there also a way to switch to ISDN if the SIP trunk is exhausted? (Where can the "capacity" of the SIP trunk and ISDN line be specified?)


thx,
david

Paolo Bevilacqua Fri, 03/05/2010 - 16:07
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