The Cisco ATA 186 is a handy little device that allows you to use all of those legacy analog telephony devices through your Cisco CallManager. It has two analog lines available but to use them each has to be setup as a device in Call Manager. The steps to setup an ATA 186/187 are located here. If for some reason following the steps in the Cisco article you can’t find the second port on the ATA as a device in CallManger you can manually set it up using the instructions below to generate the accepted MAC address.
Drop the first two nibbles of the MAC address and shift the MAC address to the left, then add 01 to the right end of the MAC address. For example 00070EA26032 is port 1 and 070EA2603201 is port 2.