Calling and Call Control
Digit analysis and the dial plan
Every dialed string is analyzed against partitions. CUCM prefers an exact match over a wildcard match, then the longest match, then the order of partitions in the calling search space; the urgent priority flag can force a pattern ahead of a longer match. Partitions group route patterns, DNs, and translation patterns; a CSS is an ordered list of partitions a device or line may dial. Critical trap: the line CSS is evaluated first and the device CSS is appended after it.
Routing constructs
Route pattern to route list to route group to gateway or trunk. Route lists search route groups top-down by default and can also distribute by circular or longest idle. Translation patterns rewrite digits and then re-route using their own CSS - the main tool for globalized plus-E.164 dial plans and site-code stripping.
Call control features
Call coverage runs line group to hunt pilot to hunt list. Call forward all/busy/no answer, shared lines, call park with recall timers, call pickup, hold, and conferencing are staples. Time-of-day routing assigns a time schedule and time period to a partition.
Worked example: put internal DNs in partition INTERNAL and PSTN patterns in partition PSTN, then give phones the CSS INTERNAL, PSTN. Any blocked pattern sits in a partition ordered first so it wins before the permitted pattern is reached.
Traps: assuming partitions are searched alphabetically; forgetting that a translation pattern with no CSS transforms digits but has no partitions to route into; confusing route list order with MRGL order.