- with regard to getting the ucm to send to the unix server with a different port for each extension (which is the correct way), do a capture of the GS phone and see how it formats the message and then try and replicate in the unix device.
- providers may have various ways of supporting calls and may use 1 trunk for each call (call path) or 1 trunk supporting multiple call paths. it is usually determined by the plan type offered/selected and the related charges.
there are typically 3 types, but maybe more:
1- 1 trunk, 1 call path. like a landline in that only one call at a time. usually a fixed monthly cost regardless of minutes used.if you need to make/receive more than 1 simultaneous call, more trunks are added. Some providers will simply leave it at one trunk and increase the number of call paths and increase the monthly fixed price accordingly.
2- plans that offer a fixed number of minutes somewhat like some cell phone plans. unlimited call paths or a larger number such that all minutes used by all calls are aggregated and counted against the plan. Usually no carryover of unused minutes and penalties for overages. Providers vary their offering somewhat but the gist of how it works is the same.Usually one trunk.
3- metered minutes. pay as you go scenario as there is typically a fixed cost per minute of usage and and unlimited or large call path. all minutes from all call are aggregated and charged at the per minute rate. Usually 1 trunk.
there are other plans which may offer a certain number of “free” minutes or local calling, but these are usually offered by ISPs who also support telephony such as Spectrum, Comcast and the like.
The number of trunks may vary as different services may be provided by a different center. providers may also have georedundant centers and you may be asked to setup added trunks for these as there are concerns about Asterisk’s ability to handle DNSsrv correctly.
if I were you, I would seriously look around and check your options. maybe you have none but 48 trunks seems like a nightmare to me.