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New Member

Call Manager Subscriber and SRST

Hi all,

I have a small problem that I would like to address with your help. As you can see in the attached scenario I have a Call Manager (Publisher) in a city (City 1) and a brand new subscriber in City 2. Previously to this scenario there was only one CCM (Publisher) in City 1 and, should the wan link fail, the phones would use the local SRST in City 2. If phones in City 2 wish to call City 1 or phones located at City 1, they go to the publisher.

The question is, in the current scenario with the new Subscriber, if the wan link failed, how could I make the phones use their local SRST in the router at City 2 so they still can make phone calls through their local PSTN?

Thanks and kindest regards,

Fer

1 ACCEPTED SOLUTION

Accepted Solutions

Re: Call Manager Subscriber and SRST

Hi Fernando,

I guess Rodrigo has cleared many of your doubts. It will be a better idea to go for load balancing. There is another benifit to it. The phone keeps communicating with the primary server with which it is registered. This it does using keepalive messages. If you register your city 2 phones with pub then all these messages will traverse across WAN eating up your bandwidth. On the other hand, if you register city 2 phones to sub in city 2, this traffic will not traverse WAN in normal case.

For configuring gateway's as Rodrigo has suggested in route patterns of city 2 partition, keep local gateway as first choice and city 1 gateway as second. In route patterns at city 1, keep it the other way.

13 REPLIES
Gold

Re: Call Manager Subscriber and SRST

You have to set up in the CallManager adminstration web pages, two SRST references and associate those references to two Device Pools, one for phones in Site 1 and the other for phones in Site two.

You have to set up in each device pool the SRST reference that applies to each site.

Hope thsi helps,

Juan Luis

New Member

Re: Call Manager Subscriber and SRST

Hi Juan Luis,

Thanks for the answer. However, I still have the problem. All those SRST configs were already done. The thing is that the phones at City 2 are registered to the local subscriber. Therefore even if the wan link is down those phones are still registered and the SRST does not kick in (please, correct me if I am wrong). If the wan link goes down, the communication between Publisher and subscriber is down, but NO in between the subscriber and the local phones (already registered to it). Will the subscriber tell the local phones at City 2 to use the local SRST for all the calls?

Once again, thanks,

Fer

Gold

Re: Call Manager Subscriber and SRST

Fer,

If the WAN link is down, the two CallManagers can not communicate, but the two CallManagers are up. So the phones can see each CallManager, for the phones, there is no failure and they continue working as if all was right.

The only way for the phones to switch to SRST is losting the comunnication with their CallManagers (all the CallManagers in the group that you hace set up).

Regards,

Juan Luis

New Member

Re: Call Manager Subscriber and SRST

Hi Juan Luis,

Thanks for the reply. So this means that they wont be able to make any phone call if the wan was down even if the subscriber was up? Talking from my ignorance: Could we play somehow with the route patterns? Since the subscriber knows when the primary is down...

The bottom line is: How would you fix this problem? They have to be able to make phone calls from City 2 regardless the problems of the wan.

Regards,

Fer

Bronze

Re: Call Manager Subscriber and SRST

Ok... looks like you have same design as me.

I have 1 publisher and 1 subscirber at Main site, and second subscriber at branch.

Since all phones (Branch phones) register subscriber at branch, so when the WAN link down, the phone still register to subscriber at branch, but they couldnt call Main site...

Also, I have MGCP gateway at branch register to subscriber.... so they still use the MGCP gateway to call out...

They trade off is that the user dont know the wan link down... they always try to call Main site by using 4 digits extension....

Hopefully, thats what you looking for...

Ken

New Member

Re: Call Manager Subscriber and SRST

Hello I have a design very close to that and I have the same problem, when the wan links fails ( and sadly that occurs too much times) the user dials the local extension and the calls are droped. Is there any way to make the internal calls redirected through the ISDN E1 gateway to the long number? I have been thinking in using AAR but I am not sure if it is going to work.

New Member

Re: Call Manager Subscriber and SRST

Hi,

Well, it seems to me like that the only answer would be to re-install the CCM in City 2 as a Publisher rather than as a subscriber and then make an intercluster between the CCM of City 1 and City 2.

Any other suggestion to this solution would be much appreciated since this would be a very drastic and dramatic change for the customer.

Kindest regards,

Fer

Re: Call Manager Subscriber and SRST

Hi Fer,

You may not need to take all this trouble actually. As Ken has suggested, you can have your T1 line at City 2 to terminate on a local gateway and then register it with the subscriber. In this scenario, even if your WAN link is down, your phones will be able to call using T1.

Since you have installed a subscriber itself you do not need SRST here. You can keep it in case this subscriber fails when WAN is down (quite unlikely, isn't it).

Apart from this, do you have DIDs in both the offices.

New Member

Re: Call Manager Subscriber and SRST

Hi,

Yes, I do have DIDs in both offices. What I can not see is how I can register the subscriber at City 2 with the local gateway there. Please, any config/white paper where I could see this?

Thanks for your time. Sincerely,

Fer

New Member

Re: Call Manager Subscriber and SRST

Hi,

Please, could you clarify what you mean by "register it with the subscriber"? Where? How?

Thanks and regards,

Fer

New Member

Re: Call Manager Subscriber and SRST

Hi,

Maybe I just found tha answer.

http://www.cisco.com/univercd/cc/td/doc/product/voice/c_callmg/4_1/sys_ad/4_1_3/ccmcfg/b06gtway.htm#wp1311093

With this I install the Subscriber at City 2 with the City 2 router as the gateway. Should the link between city 1 and city 2 go down I presume that all the calls would go through the router-gateway at City 2, right? Please advice.

Regards. I appreciate your time with this,

Fer

New Member

Re: Call Manager Subscriber and SRST

Fernando,

i think that you would preffer to put the Subscriber like the second option, and the SRST as the third option.

Have you think to do the load balancing between both CM??, in CM Group you must create 2 groups: 1:Pub/Subs and 2:Subs/Pub. Later in the Dev Pool you must create two of it: one with the Group1 and the other with Group2, then the Phones in the City1 -> Dev Pool1, and City2 -> Dev Pool2. Remember to use the IP Addresses of the Servers.

The idea is if one Server die the other take over all the proccess, and if the WAN die, both manage the phones in its own city.

For the calls you must create both VGW and make two route group (City 1 & City2) and two route list (City1/City2 & City2/City1)

Good Luck and Best Regards

Rodrigo

Re: Call Manager Subscriber and SRST

Hi Fernando,

I guess Rodrigo has cleared many of your doubts. It will be a better idea to go for load balancing. There is another benifit to it. The phone keeps communicating with the primary server with which it is registered. This it does using keepalive messages. If you register your city 2 phones with pub then all these messages will traverse across WAN eating up your bandwidth. On the other hand, if you register city 2 phones to sub in city 2, this traffic will not traverse WAN in normal case.

For configuring gateway's as Rodrigo has suggested in route patterns of city 2 partition, keep local gateway as first choice and city 1 gateway as second. In route patterns at city 1, keep it the other way.

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