Busy Lamp Field (BLF) and Unified Attendant Console (CUxAC)


Product Overview

CUxAC is a replacement product for the now defunct Attendant Console plug-in application that was embedded into pre-8.x releases of CUCM.  The CUxAC product options are Cisco OEM versions of a 3rd-party application offered by Arc Solutions. Unlike the legacy plug-in AC application, CUxAC must be deployed on a separate server and there are three versions available to meet different requirements.

  • Cisco Unified Department Attendant Console (CUDAC) supports up to 5 queues (1 per department), up to 10 operators (2 per department), and 750 contacts.
  • Cisco Unified Business Attendant Console (CUBAC) supports up to 3 queues, up to 6 operators, and 500 contacts.
  • Cisco Unified Enterprise Attendant Console (CUEAC) supports up to 50 queues, up to 25 operators, and unlimited contacts. 

Note: This list only provides basic product limitations.  Other considerations may apply based on specific requirements.

Installation Details

Some details pertinent to my experience with this issue:

  • CUCM 8.5(1) SU3
  • CUBAC 8.6(2)
  • Flat address (10-digit) dial plan
    • Modular, flexible, highly scalable
    • Directory numbers are configured as 10-digit numbers
    • Supports abbreviated dialing (e.g. 4-digits)
  • CUCM is integrated with LDAP for directory synchronization
    • The ipPhone attribute contains an abbreviated 4-digit extension and is used to populate the Telephone Number field for CUCM End Users
    • Supports abbreviated dialing display and functionality for Corporate Directory


After installing and logging into the Operator Console, the following issues were observed:

  • BLF status for contacts does not display (i.e., status icon displays a red X)
  • The device name details for contacts is not populated

Root Cause

The telephone number for a contact in CUxAC must EXACTLY match a directory number in CUCM. 

Note:  CUxAC pulls directory information from CUCM via AXL.  In my specific configuration, the contact telephone numbers in CUxAC are pulled from CUCM as 4-digit extensions but the directory numbers assigned to IP phones are configured as 10-digit numbers in CUCM.   Since the contact telephone numbers do not match directory numbers in CUCM, BLF does not work.

There are other scenarios where this could be problematic.  A very simple, but likely common, scenario would be one where telephone numbers are formatted for display purposes (e.g., XXX-XXX-XXXX).  In this case, the contact telephone numbers in CUxAC would be formatted with a dash so they would not match directory numbers in CUCM.  After researching this issue, I should also point out that this appears to be applicable to the application in general.  In other words, it is not specific to the Cisco OEM versions.

Options / Workarounds

A quick list of options/workarounds and considerations includes:

  • Don’t use BLF
    • It may not be ideal but, for some customers, this may be a valid option.
  • Manually enter the device name (i.e., for IP phone) for each contact in the Operator Console
    • This works but it lacks scalability.
    • In my scenario, there were two separate console installations and several hundred contacts in the directory.  So, you have to enter this data manually for each console installation.  In addition, you also have to consider how regular maintenance tasks such as moves, adds, and changes impact the viability of this option.
  • Ensure that contact telephone numbers match directory numbers in CUCM
    • This directly addresses the issue; however, it may have additional impact.
    • In my scenario, this would directly impact Corporate Directory functionality and introduces a need for implementing a custom directory application.
    • Do you need to update telephone numbers to remove formatting?

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Nick Kelly

Cybersecurity Engineer, Cisco

Nick has over 20 years of experience in Security Operations and Security Sales. He is an avid student of cybersecurity and regularly engages with the Infosec community at events like BSides, RVASec, Derbycon and more. The son of an FBI forensics director, Nick holds a B.S. in Criminal Justice and is one of Cisco’s Fire Jumper Elite members. When he’s not working, he writes cyberpunk and punches aliens on his Playstation.


Virgilio “BONG” dela Cruz Jr.

CCDP, CCNA V, CCNP, Cisco IPS Express Security for AM/EE
Field Solutions Architect, Tech Data

Virgilio “Bong” has sixteen years of professional experience in IT industry from academe, technical and customer support, pre-sales, post sales, project management, training and enablement. He has worked in Cisco Technical Assistance Center (TAC) as a member of the WAN and LAN Switching team. Bong now works for Tech Data as the Field Solutions Architect with a focus on Cisco Security and holds a few Cisco certifications including Fire Jumper Elite.


John Cavanaugh

CCIE #1066, CCDE #20070002, CCAr
Chief Technology Officer, Practice Lead Security Services, NetCraftsmen

John is our CTO and the practice lead for a talented team of consultants focused on designing and delivering scalable and secure infrastructure solutions to customers across multiple industry verticals and technologies. Previously he has held several positions including Executive Director/Chief Architect for Global Network Services at JPMorgan Chase. In that capacity, he led a team managing network architecture and services.  Prior to his role at JPMorgan Chase, John was a Distinguished Engineer at Cisco working across a number of verticals including Higher Education, Finance, Retail, Government, and Health Care.

He is an expert in working with groups to identify business needs, and align technology strategies to enable business strategies, building in agility and scalability to allow for future changes. John is experienced in the architecture and design of highly available, secure, network infrastructure and data centers, and has worked on projects worldwide. He has worked in both the business and regulatory environments for the design and deployment of complex IT infrastructures.