Cisco 300-815 CLACCM: Call Control and Dial Planning

Domain 1 - Call Control and Dial Planning

Call Control and Dial Planning is the largest slice of 300-815 (25%). It tests whether you can build a CUCM dial plan whose digits, partitions, and transformation steps do exactly what the business intends - on-net, off-net, and at the PSTN edge.

Building blocks

• Partitions group route patterns, translation patterns and directory numbers; a calling search space (CSS) is an ordered list of partitions. Digit analysis walks the CSS partition by partition and stops at the first match - there is no longest-match contest across partitions.
• Route group → route list → route pattern. Route groups list gateways with a top-down or circular distribution algorithm; route lists order route groups for failover.
• Translation patterns are a routing step (they can mask digits and hand the call to a new CSS); transformation patterns are reusable masks invoked through a transformation CSS.

Digit manipulation

• Prefix digits (add), strip digits (remove from the left), external phone number mask (caller-ID presentation), and discard digits using the pre-dot notation, which drops only the digits before the dot at that hop.
• Wildcards: X = 0–9, ! = one or more digits, @ = the North American Numbering Plan, [] and - = digit ranges, ^ = any non-digit character.

Worked example

A user dials 9-1-214-555-1234. The line CSS contains partition PSTN-ACCESS, which holds route pattern 9.@ with discard digits set to pre-dot, assigned to route list RL-PSTN (RG-PRI first, RG-SIP second). Digit analysis matches 9.@, discards the leading 9, and offers 12145551234 to the route list; the PRI group is down, so the list rolls to RG-SIP. The SIP trunk's outgoing calling-party transformation then adds +1 so the provider sees E.164. Reasoning check: if an earlier partition in the CSS held a translation pattern matching the same digits, that pattern would win and 9.@ would never be evaluated.

Traps that cost marks

• Confusing strip (always removes from the left) with pre-dot discard (only the pattern's leading digits, only at that hop).
• Assuming CUCM chooses the most specific pattern; it chooses the first match in CSS order.
• Forgetting that @ also covers emergency and operator numbers such as 911 - a classic toll-fraud hole.
• Setting a calling-party transformation CSS on the phone but not on the trunk, so globalized +E.164 caller ID is lost at the PSTN edge.
• Expecting a route list to fail over when Enable This Route List is unchecked.