We have a client using Call Manager 5. There are 2 types of users. First type is admin and they dial 0 to get an outside line. The second type is the residents of the facility who have direct access to the PSTN. Route patterns are configured using route filters based on the Australian numbering plan. The issue here is when the residents try to call each other using the last 4 digits which is their extension. It dials but takes around a minute to connect. This is because of the inter digit timeout i guess. Looks like the phone is expecting more digits but when it finds none dialed, it places the call to the extension. This does not happen when the admin phones are trying to call the residents. I believe this is because all numbers they dial are prefixed with 0 whereas the apartment extensions are in the range 80XX.
even if you try to configure 80XX that would be the same thing, 8XXXXXXX covers that pattern
what you could possibly try is to use a translation pattern to modify the DIDs, for example if you do not use 7 for outside dialing or any other internal use configure a translation pattern for the 80XX pattern and change that into 70XX.
of course this would mean to change the whole internal extensions to a 70XX instead of 80XX
outside callers would not notice any change in the way they dial, this would only affect internal dialing.
add a prefix to the number and have 5 digit extensions is also a way to do this
Avoiding Overlap of Extension Dialing
as i mentioned what's explained in our SRND is the guideline to a good dial plan design.
if you fall on the overlapping then the consequences are the interdigit timeout and that is WAD.
the only way to get rid of it is to change the dial plan, change the internal DNs or have users dial extradigits for the outside calls pressing something else than 8 for the 1st digit
if this helps, please rate