[cisco-voip] CCM4.1, Gatekeeper and tech prefix routing

[Wes Sisk]

possibly gktmp?

Andre Beck wrote:

>Hi,
>
>I've got a network of several H.323 gateways (IOS, currently running
>CCME) and a central gatekeeper to which they all nicely register their
>phone numbers, allowing me to do dynamic call routing even with a random
>(non-hierarchical) dial plan the organization uses and needs to stay
>with. The gatekeeper is also a gateway (registering to itself) and besides
>running CCME it has the E1 egress point to the PSTN as a dialpeer.
>
>Now this architecture is beeing merged to a central CCM 4.1 cluster
>with all the former CCME gateways beeing turned into SRST gateways.
>I plan to stay with the gatekeeper so if CCM fails altogether, the
>phones will register to their respective SRST gateways, the gateways
>will register the phone numbers to the gatekeeper and given that they
>are still reachable, call routing will continue to work.
>
>Sadly enough, CCM has a major flaw IMO: It doesn't register the numbers
>it knows about to the gatekeeper. I've got the gatekeeper and trunk set
>up perfectly, the CCM registers, but the GK doesn't know what numbers
>are there. I've read docs up and down and assume that is the way it is -
>no option to activate number registration anywhere (probably a scalability
>issue).
>
>Now the basic question is: How does the gatekeeper decide which unknown
>(not registered) number is routed to which gateway? The tech support
>proposes to use tech prefixes and the IOS GK feature "default-technology"
>which essentially defines a default route for all unknown numbers towards
>the gateway with a certain tech prefix. In the trivial setups shown in
>these tech papers, this is sufficient.
>
>My problem: It is not sufficient here, as I have *two* kinds of unknown
>numbers, and they have to be routed to *different* gateways: The numbers
>that should be routed to the PSTN (must be routed to the gateway that
>also happens to be the gatekeeper) and the remaining numbers (must be
>routed to the CCM). They are easy to differentiate from each other, the
>PSTN directed ones all start with 0 (this is not the NANP), but I don't
>find a way to tell this to the gatekeeper. I could direct them to another
>zone easily, but they are not going to another GK, they are simply to
>leave the IP world alltogether.
>
>Now what I did for a partial solution:
>
>1) The gateway with the PSTN dialpeer registers with another tech
>   prefix than the CCM. Say CCM registers with 1#* while the gateway
>   registers with 2#*
>2) In every route pattern on the CCM that routes 0-starting numbers
>   towards the gatekeeper trunk, I prefix the called party number
>   with 2#
>3) On the gateway, the dialpeer destination is changed from 0T to 2#0T
>
>The good thing: This works. It routes exactly as intented.
>
>The bad thing: The phones change the display of the called party number
>from 0xxxxx to 2#0xxxxx which looks weird and disturbing. It is correct
>and more of a cosmetic issue, but I can't deploy it this way. So is there
>a way to do this without having the display change? Ideally there would
>be a special tech-prefix option in the route pattern as is in the voip
>dialpeer on IOS, but I only found the explicit prefix.
>
>Long question, but I spent hours on it, either. Any comments are
>welcome. This includes comments on whether a setup as described
>(GK for dynamic routing to SRST gateways) is feasible or going
>to work at all...
>
>TIA,
>Andre.
>  
>