DMA OperationsGuide Dial Rules
248 Polycom, Inc.
•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 page109 a nd “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.