[cisco-voip] Call Routing (Loop)

lelio at uoguelph.ca lelio at uoguelph.ca
Tue Jun 30 21:23:03 EDT 2009


Daniel has it spot on. The incoming calling search space of any trunk/ 
gateway/gatekeeper/etc should not include any partition that contains  
any route pattern that would end up routing a call back to itself.



Lelio Fulgenzi, Senior Analyst
Computing & Communications
University of Guelph
519-824-4120 x56354

...sent from my iPod - please pardon my fat fingers ;)

[XKJ2000]

On 2009-06-30, at 7:46 PM, Daniel <dan.voip at danofive.id.au> wrote:

>
> We had a very similar issue to this, ended up being that CSS was  
> configured wrong on our trunk to our gatekeeper.
>
> A call would come in from our external gateway or an internal call,  
> the externsion could not be found so the call would match the catch  
> all route pattern and go out the trunk to the gatekeeper. The  
> gatekeeper would have the correct zone prefixes and send the call  
> back to the same zone it came from. The inbound CSS of the  
> gatekeeper trunk had the wrong CSS configred which allowed calls to  
> go back out to the tieline which created a loop as call manager set  
> the call back to the gatekeeper and the gatekeeper sent the calls  
> back to the same call manager.
>
> I would advise to make sure that your gateways and gatekeepers are  
> only allowed to call internal extensions only, or at least the  
> gatekeeper so that itself is only allowed to call internal extensions.
>
> The call will still hit the gatekeeper once but when the call comes  
> back in from the gatekeeper to the call manager the call is  
> rejected, the extension can not be found and there is no partition  
> in the css that allows access to the route pattern for the trunk.
>
>
>
>
>
> On Wed, Jul 1, 2009 at 7:59 AM, Scott Voll <svoll.voip at gmail.com>  
> wrote:
> I don't think I follow all of scenario 2 but as for #1 we had the  
> same thing with our old PBX and our CM.  if the extension wasn't on  
> either system you would loop until all channels were in use or  
> someone disconnected.  I think the only fix would be to have a RP  
> with all the extensions not in use forwarded to an AA.  But every  
> time you move an extension over you will need to delete the RP  
> extension.  If you were doing a trunk and not a channel based  
> circuit to the other PBX you have the ability to kill the system  
> because it will keep looping until the system can't take it any more.
>
> Scott
>
> On Tue, Jun 30, 2009 at 12:47 PM, <steve.siltman at assurant.com> wrote:
>
> Here is a couple of scenarios that I need help with.
>
> Scenario 1:
> Cisco IP Phones and Avaya phones mixed at the same location.  MGCP  
> router is the go-between.  If an extension is dialed and doesn't  
> live on one system, it forwards the call to the other system.  This  
> works great.  What if the extension doesn't live on either system?   
> I was taking a trace from Call Manager, on a different issue, and  
> noticed a problem that looks like a call is doing the above.   
> Without adding specific route patterns and continuing to use a large  
> 1XXXX pattern to send calls across to Avaya when they don't exist on  
> Call Manager, can I limit this route loop or stop it from happening  
> somehow?
>
> Scenario 2:
> This one has me perplexed because I'm not sure why I didn't notice  
> this long ago or how it continues to loop.  The call comes into a  
> remote H.323 gateway and the DNIS is translated into a DN that lives  
> on Call Manager.  The dial-peer looks up the DN on Call Manager but  
> it doesn't exist. *sigh*  We have a route pattern configured to  
> point all those extensions towards the remote H.323 gateway.  I  
> believe the first office was setup this way and its been copied for  
> each additional remote office install.  We now have 20 offices that  
> have a route pattern pointing the Internal DN range back out to the  
> remote H.323 gateway where the phones live physically.  I believe  
> the resolution to this is to remove these internal DN range route  
> patterns.  Call Manager already knows them and doesn't need this  
> route pattern.  Correct?   I still don't understand how this could  
> be looping but it must be looping within the Call Managers.  I  
> turned on ISDN Q931 and VOIP DIALPEER debugs on the router and saw  
> the call come in and hit the dial-peer to Call Manager.  Thats all I  
> saw on the router but yet the Call Manager had 250 trace files, each  
> 1 meg in size and rolled after 9 minutes.  Digit analysis shows the  
> called number and the extension, that doesn't exist, over and over  
> and over in just under 1 second intervals.  I'm pretty sure removing  
> this internal DN range route pattern will resolve this but I'd like  
> to know how its looping.
>
> Any suggestions or you've seen this before would be appreciated.   
> Thanks!
>
> Steve Siltman
> Assurant Corporate Technology
> steve.siltman at assurant.com
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