Lets see if I can explain this...
You can have different types of partitions;
PT_LD - assign this to the route pattern for LD Calls
PT_Local - assign this to the route pattern for 7/10 digit calling
PT_International - assign this to international calling
PT_Internal - assign this to your lines for internal calling between phones
Then you can have different types of CSS as well... the PT's reside in a CSS
CSS_LD_Ability - PT_LD, PT_Local, PT_Internal
CSS_NO_LD - PT_Local, PT_Internal
CSS_Intl_Ability - PT_LD, PT_Local, PT_Internal, PT_International
Each gateway, line, route pattern, ect will have a PT assigned to it.. This allows you to control what phones can call what devices/route patterns. You can have voicemail partitions, so if you do not want specific users in a certain CSS to call the VM group you can.
Another way is to give the actual phone ability to call everything, then restrict the line from calling international by creating a CSS that blocks international calling.
Now that the examples are out of the way... Partions allow a devices to call other devices in the same partitions. CSS allow you to group Partitions together so that a device can access other partitions that are not assigned to it specifically.
Hope this helps
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Dallas, Texas
Telecommunications Tech
CCVP, CCNA, Net+
CCNP in the works