15 Virtualization: Cucm

Always ensure the VM is using the VMXNET3 network adapter type. This is a para-virtualized network driver designed specifically for high performance in VMware environments.

The deep implication here is the elimination of overcommit. In traditional IT, virtualization’s economic benefit comes from oversubscription of CPU and RAM. CUCM 15 explicitly forbids this for production nodes. For a 10,000-user subscriber node, the SSM might mandate 8 vCPUs with 8,000 MHz of reservation and 32 GB of reserved RAM. This is not a suggestion; it is a support boundary. Cisco’s real-time kernel (based on the Precision Time Protocol – PTP) requires deterministic scheduling. If a hypervisor scheduler preempts a CUCM vCPU to service a print server or a development VM, call setup latency spikes, media resources glitch, and CDR logs become corrupted. cucm 15 virtualization

The team then began deploying the virtualized CUCM 15 environment. They: Always ensure the VM is using the VMXNET3