Hi guys I have two buildings both buildings are on the same network same location the are connected with fiber. In building A I have the ip500v2 and in building B I have a ip400v4.2. On the ip500 the extensions are 3xxx and in the ip400 they are 4xxx. The problem I'm having is I'm not able to login into a 3xxx extension from building B nor can I login to a 4xxx extension from building A. The system is able to call from A to B and B to A. How can I fix it where I can login to any phone with any extension either 4xxx or 3xxx?