Polycom 3725-76302-001LI manual 248

DMA Operations Guide Dial Rules

•To add an MCU, ISDN gateway, SBC, neighbor gatekeeper, SIP peer, or simplified dialing service that can be dialed by prefix, configure the prefix range of the new service on the appropriate page. No dial plan change is necessary, since Rule 4 of the default dial plan takes care of dialing by prefix.

•You can remove or disable a default dial rule if you don't want the associated functionality. But note that Rule 6 (Dial endpoints by IP address) is used in several scenarios where calls are received from neighbor gatekeepers or SBCs. Removing it breaks these scenarios.

•If certain dial strings are matching on the wrong dial rule, you may need to re-order the rules.

•In some circumstances (depending on the dial plan and the network topology and configuration), dial rules using the Resolve to external address action (like Rule 5 of the default dial plan) or the Resolve to IP address action (like Rule 6) can enable dialing loops to develop, especially if servers reference each other either directly or via DNS.

Common ways to avoid dialing loops include:

—Use domain restrictions to ensure that the DMA system and its peers are each responsible for specific domains (see “Add External SIP Peer Dialog Box” on page 109 and “Domains” on page 242).

—Use a preliminary script like the sample script “SUBSTITUTE DOMAIN (SIP)” (see “Sample Preliminary and Postliminary Scripts” on page 258) to change the domain of a SIP URI dial string to something that won’t create a dialing loop.

—Use a postliminary script to similarly change the domain before sending to a peer.

—Use configuration options on the peers to prevent loops.

•You can add a filtering preliminary script to any dial rule to restrict the behavior of that rule.

For example, if you know that all the aliases of a specific neighbor gatekeeper are exactly ten digits long, you may want to route calls to that gatekeeper only if the dial string begins with a certain prefix followed by exactly ten digits.

To accomplish this, add a preliminary script to the service prefix dial rule that rejects all dial strings that begin with the prefix, but aren’t followed by exactly ten digits.

•To exclude certain dial strings, combine a filtering preliminary script with the Block action.

•You can use a preliminary script to modify the dial strings accepted by any of the rules.

248 Polycom, Inc.