Polycom RealPresence Collaboration Server (RMX) 1500/2000/4000 Administrator’s Guide
19-10 Polycom, Inc.
Calling an IP Endpoint via Gateway
If the call destination is an IP endpoint, the endpoints must be registered to the same
gatekeeper to which the RMX is registered. There should be a mapping between the dial-in
numbers in the range defined for the ISDN Network Service and also assigned to the
Gateway Profile and the IP endpoints, in such a way that the alias of each endpoint is the
number that will be appended to the ISDN prefix.
When the call arrives to the gateway, this prefix is truncated and replaced by digits that
correspond to the MCU prefix in the gatekeeper and the call is forwarded to the destination
endpoint.
Figure 20 Call Flow from ISDN Endpoint to H.323 Endpoint with Automatically
Generated Forwarded Dial String
For example:
• The ISDN prefix is 9251.
• The dial in number range defined in the ISDN Network Service can be 100 to 400 (that
is, 9251100 to 9251400).
• The dial in numbers assigned to the Gateway Profile can the entire range, or part of the
range of other Gateway Profiles are to be used: 100 to 200 (that is 9251100 to 9251200).
• The aliases assigned to the IP endpoints will range between 100 to 200 or 400 (for the
full range) as well.
• MCU Prefix in the gatekeeper: 79.
• Number of digits to append (same as the ISDN prefix is this example): 3.
• The destination endpoint alias is 123.
• The ISDN endpoint dials 9251123. The RMX truncates the four first digits 9251
replacing them with 79 and appends 123 to 79, to create the destination number 79123
which is sent to the gatekeeper for routing.

Interoperability with CMA

The RMX does not register to the gatekeeper as a Gateway, therefore it is recommended to
create and use the CMA Dialing Rules to enable the CMA Dial One Method.
When the caller enters the Dial One digit as the destination number prefix, the CMA
replaces this digit with the MCU prefix in the Gatekeeper and the ID of the Gateway Profile.
For example, the calling participant can enter 99251444, where 9 is the digit that is used as
the MCU prefix registered in gatekeeper and is replaced by the gatekeeper with * and the
Gateway Profile ID (for example, *2000) as defined in the Dialing Rule.