I'm having some difficulty with dialing conventions in H323 and am hoping to find some assistance.
I have a CUBE/Gatekeeper in the DMZ with firewall rules to allow H323 communication w/ the GK. I have internal video endpoints registered to the Gatekeeper. I have other SCCP Tandberg endpoints, registered to UCM, which are reachable via a Gatekeeper controlled trunk.
I need external endpoints (not registered to any Gatekeeper) to be able to dial into the Gatekeeper and hit the internal endpoints which are registered to the gatekeeper or UCM. I have been able to do this successfully with some older endpoints (T1000 and Polycom PVX), using the convention 10.10.10.10##1234 where 10.10.10.10 is the Gatekeeper and 1234 is the registered endpoint's E.164. Newer endpoints (e.g. Tandberg C40) do not appear to accept this dialing convention. Further, the URI dialing (e.g. [email protected]) support in clients appears to be spotty. I need to be able to dial the endpoint directly from external endpoints. More importantly, I need to be able to document a way for my customer's outside relationships to dial into various endpoints.
What are the generally accepted dialing conventions used for this type of calling? What I'm finding so far appears to be somewhat inconsistent in terms of endpoint support.
I have also used the null number override feature from this doc: <http://www.ciscosystems.lt/en/US/products/sw/voicesw/ps5640/products_configuration_example09186a0080b091e2.shtml>, to send callers into an IVR where they can select their endpoint to be transferred into via a UCCX or Unity menu; however, in this instance, I am implementing this project for a school for the deaf, so an audio menu is not an option.
I also realize that typically direct NAT translation to various endpoints with individual IPs would be another way to handle this; however, since some endpoints are Tandbergs running SCCP (I can't change them over to H323 because the cust is out of support), and will only call through UCM and Gatekeeper.
There is not a solution on the cisco side but VCS implements a feature called "FindMe" that would allow the user to dial @ which in turn could be aliased by the FindMe feature to for an H.323 gatekeeper look up or @ to make a SIP based look up. The reason for using the FindMe feature is to address what your customer has discovered: H.323 endpoints don't typically recognize @ as a URI/Annex O address. When presented with such a string, instead of doing an SRV record look up on the domain to find the appropriate call control agent, they do an A record lookup of the full string. This isn't a problem for SIP endpoints but the aliasing technique then results in an address that any outside caller would be able to use.
That would get the call into the environment but there are challenges to returning the call. IOS gatekeepers don't support Annex O/URI dialing and native cisco CUCM endpoints don't either. To deal with that, the customer could use VCS for their internal H.323 endpoints. There currently isn't a fix for the UI issues of cisco CUCM entities but FWIW, third party SIP endpoints registered to CUCM can in fact dial URI's and if one configures the appropriate SIP route pattern in CUCM, you can in fact allow them to return a call dialed by URI.
At this point cisco only supports uri based dialing the only workaround we have for ip based dialing is the null number overide. What you already implemented is what is our best solution at this point. Basically null number be translated to some number send it to the cube that has invia zone enabled that will send the call to the GK and the GK will route it to some unity AA. In any ways let me find out if support for ip+ dialing is in the near furure or not.