I recently encountered a strange problem where calls to certain test numbers stopped working as expected after we’d commissioned a new Sonus PSTN Gateway for Lync (in this case an SBC1k running 3.0.2 b271 firmware) “upstream” from the PABX.
If you called ”127 22123” from the PABX, the call just rang and rang without answer – where it should have answered instantly and spoken your CallerID back to you. (This service has lost much of its relevance of late simply because it’s just as easy to call your mobile and view the CallerID on screen, adding the 1832 prefix if the line’s normally set to hide its details by default).
Installing the Gateway “Upstream”
Just in case you’re not familiar with the scenario, let me fill in some background.
As a first step to ease an Enterprise Voice customer into Lync, we’ll often commission their new PSTN Gateway “upstream” of their PABX, and we do so just by breaking their existing ISDN service to the PABX and re-routing it through the gateway. It’s often as simple was re-routing a patch cord, although you’ll need an ISDN crossover like one of these guys for one leg.
As far as the PABX is concerned it still thinks it’s talking to the carrier, whilst to the carrier the gateway emulates a PABX.
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