CUCM: Calling Search Space and Partition examples

This is a re-write of Understanding calling search space and partition, I attempt to simply it and give examples.

Partition

Partition is to group entities together. Entities are directory numbers, route pattern and translation pattern.

Directory numbers are group together by assigning the route partition. Grouping entitles together does not restrict call flow, to restrict and control call flow you need calling search space.

Call Search Space (CSS)

Calling search space specifies which partition can the assigned IP phone calls to. All created CSS has none partition, but none CSS only has none partition hence phone assigned to none CSS cannot call to any phones assigned to created partitions, phones assigned to created partitions however can call to phone assigned to none CSS.

Example 1:
BLUE-CSS = BLUE-PARTITION
XOVER-CSS = RED-PARTITION + BLUE-PARTITION
RED-CSS = RED-PARTITION

Directory numbers: 1000 (XOVER-CSS, BLUE-PARTITION), 1001 (RED-CSS, RED PARTITION), 1002 (none CSS, none partition)

1. 1000 can call 1001, because XOVER-CSS HAS RED-PARTITION. 1001 can call 1002 because XOVER-CSS has implicit none partition.

2. 1001 cannot call 1000, because RED-CSS does not have BLUE-PARTITION. 1000 can call 1002 because RED-CSS has implicit none partition.

3. 1002 cannot call to 1000 and 1001, because none CSS does not have RED-PARTITION and BLUE-PARTITION, none CSS only has none partition hence 1002 can only call to directory numbers that are assigned to none partition.

Example 2:
MOBILE-PARTITION = 9.[86]XXXXXXX
XOVER-CSS = RED-PARTITION + BLUE-PARTITION + MOBILE-PARTITION
BLUE-CSS = BLUE-PARTITION
RED-CSS = RED-PARTITION
NOMOBILE-XOVER-CSS = RED-PARTITION + BLUE-PARTITION

Directory numbers: 1000 (XOVER-CSS, BLUE-PARTITION), 1001 (RED-CSS, RED-PARTITION), 1002 (none CSS, none partition), 1003 (NOMOBILE-XOVER-CSS, BLUE-PARTITION)

1. 1000 can call out to mobile telephone (eg. 9XXXXXXX or 8XXXXXXX) because XOVER-CSS has MOBILE-PARTITION which has the route pattern. 1000 can call to 1001 because XOVER-CSS has RED-PARTITION, 1000 can call 1002 because XOVER-CSS has implicit none partition.

2. 1001 cannot call 1000 and 1003 because RED-CSS does not have BLUE-PARTITION. 1001 cannot call out to mobile telephone because RED-CSS does not have MOBILE-PARTITION. 1001 can call to 1002 because RED-CSS has implicit none partition.

3. 1002 cannot call to 1000,1001 and 1003 because none CSS only has none partition, 1002 can only call to directory numbers in none partition. 1002 cannot call to mobile telephone because it does not have MOBILE-PARTITION.

4. 1003 can call to 1000 because NOMOBILE-XOVER-CSS has BLUE-PARTITION, 1003 can call to 1001 because NOMOBILE-XOVER-CSS has RED-PARTITION, 1003 can call to 1002 because NOMOBILE-XOVER-CSS has implicit none partition, 1003 cannot call to mobile telephone because NOMOBILE-XOVER-CSS does not have MOBILE-PARTITION.

Conclusion
1. Cisco recommends not to use none partition and none CSS, it is stated clearly but not obviously in Cisco doc. The networking nerd will slap you if you use none for everything.

2. If your directory number resides in none partition, any phone in any partition using any CSS can call your directory number. But your directory number cannot call to other directory numbers reside on other partitions.

3. Partition defines the group of entity, no control will be implemented if CSS is not created. Take partition like ACL statement, without applying on an interface (either ingress or egress) ACL has no effect.

4. CSS determines which partition your directory number can call to.