Let's say Callmanager 4.2 at Head office. HO has 4xxx and one branch has 5xxx extensions. Both have PSTN connection. And route plan is setup, so when WAN is down PSTN will be use.
User from HO with 4111 moves to the branch. Callmanager knows that extension 4111 has a branch IP. So head office can call 4111 no problem.
Then the WAN link between branch and HO is down. How can HO users call 4111? Will Callmanager use route pattern 4xxx(use PSTN) to connect 4111? If so, Then nobody can access 4111, right?
How about if AAR is also configured?
I doubt it, as CallManager will most likely fail to match route pattern. You will most likely have to point to the main number and have the customer enter the extension.
HTH, please rate all posts!