Just found out that if you have several external numbers in a ring group, the total number of those get matched against the Outbound Concurrency Limit of the extension you call the ring group from.
In other words, if the Outbound Concurrency Limit of your extension is 3, and you have 4 external numbers in the ring group you are calling, you will get a “your simultaneous call limit has been reached” message and the call will fail.
Doesn’t really violate the rule of least astonishment for me. Each of these new calls is an outbound call and the extension is controlling it, so …
I get what you’re saying, there should be a way around it. Of course, ring groups with external numbers are fraught with all kinds of other perils. We’ve seen lots of problems with people connecting ring groups to external numbers including things like DAHDI phones or FAX detection shutting down the ring-group.