Cucm 15 Virtualization Link

If you are moving from CUCM 10.x, 11.x, or 12.x to version 15:

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. cucm 15 virtualization

The most common performance bottleneck in CUCM virtualization is disk I/O. If you are moving from CUCM 10

Requirements remain largely consistent with version 14, generally requiring at least 2 vCPUs for standard deployments. Deployment Size Small (150–1,000 users) Medium (2,500–7,500 users) Large (10,000 users) (Specifications based on) 3. Upgrade and Migration Considerations First, it enforces adapters over the legacy LSI Logic

CUCM 15 addresses this with two key virtualization-aware enhancements. First, it enforces adapters over the legacy LSI Logic. PVSCSI reduces CPU overhead for high-IOPS workloads, which is critical during the "BAT import" of 20,000 phones or the nightly backup. Second, the platform now supports vSphere High Availability (HA) , but with a crucial caveat: database-level replication supersedes hypervisor-level failover. If a host fails, vSphere HA will restart the CUCM VM on a surviving host. However, the database’s Automatic Disaster Recovery (ADR) mechanism must first quiesce and replay transaction logs. The essay-worthy point is that CUCM 15’s documentation explicitly recommends against using vSphere FT (Fault Tolerance), as the lock-step execution introduces unacceptable network jitter. This reveals a profound truth: virtualization provides infrastructure resilience , but application-level clustering (the CUCM database ring) remains the sovereign mechanism for call control continuity.

No deep essay on CUCM 15 virtualization would be complete without addressing the licensing paradox. Cisco has moved to a Smart Licensing model, where the VM checks in with Cisco’s cloud portal every 30 days. This means your virtual CUCM is now tethered to an external identity. While this prevents license dongles, it introduces a new failure mode: a call processing outage due to a firewall block or a Cisco licensing server outage? (Cisco provides a 90-day grace period, but the anxiety remains).