During a recent Lync 2013 Enterprise Voice roll-out I was configuring interoperability with the legacy Nortel CS1000 PBX. For this, we’d deployed a pair of Sonus SBC 1000 gateways with 2x ISDN PRI ports each. In each gateway, one PRI port was connected to the PSTN and the other PRI port was connected to the CS1000, so these gateways were deployed in an upstream model in front of the PBX.

Calls to all destinations (Lync, the CS1000 and the PSTN) were connecting fine with no media problems, but we did observe that calls from Lync to legacy PBX phones were not displaying the calling number (or caller ID, or CLI, take your pick) on the handset. Tracing this using Sonus LX found that the gateway was configured to pass through the calling and called numbers correctly, so the problem wasn’t immediately apparent: Continue reading →