You are designing a high-availability solution for Cisco Expressway. Which element is required to load-balance traffic between multiple Expressway nodes?
Cisco Expressway clusters do not natively distribute inbound signalling across nodes; an external load balancer is required to spread traffic between them. This satisfies the high-availability load-balancing requirement, since DNS round-robin alone cannot health-check or evenly balance the Expressway nodes.
Why this answer
To load-balance traffic across multiple Expressway nodes (e.g., Expressway-C or Expressway-E clusters), an external load balancer is required because Expressway does not provide built-in load balancing. The load balancer distributes incoming connections across the nodes for scalability and high availability.
Exam trap
CLCOR often tests the misconception that DNS Round Robin or built-in clustering provides load balancing for Expressway, when an external load balancer is mandatory for true HA and scalability.
How to eliminate wrong answers
Option A is wrong because Cisco CUBE redundancy is for voice gateways and SIP trunk high availability, not for Expressway clustering. Option B is wrong because a Cisco UCM Group is a CUCM concept for phone registration redundancy, not for Expressway load balancing. Option D is wrong because DNS Round Robin alone is not sufficient for Expressway high availability; it does not perform health checks or session persistence, and Expressway requires a proper load balancer for clustering.