Now That Cisco UC Only Supports Virtualization, What Should You Know?


June 4, 2014

With the release of Cisco Unified Communications Manager 10.0(1) and later, Cisco only supports virtualized deployments of Cisco Unified Communications Manager (CUCM) on a Cisco Unified Computing System server, or on a Cisco-approved third-party server configuration. This means that the large number of customers still operating on MCS servers will not be able to migrate to the latest release without an upgrade/migration strategy.

Due to the requirement of virtualization for CUCM 10.0 and above going forward, I think it’s important that customers understand how to appropriately size Cisco UC on VMWare ESXi hosts and what virtualization features are supported.  Also, it’s important that customers understand what level of virtualization licensing is required and where a more advanced license of VMware is required.


Here’s What You Need to Know About Cisco UC Only Supporting Virtualization: 

1)   Cisco only supports the virtualization of the Unified Communications applications on VMware vSphere ESXi up to version 5.1, at this time.  Microsoft HyperVisor is not supported.


2)   When preparing to migrate your Cisco Unified Communications applications from the physical host to a virtual host, it’s critical that you make sure the VMware ESXi physical host is sized correctly.


This essentially boils down to having the correct amount of virtual CPUs (vCPUs) that are available (vDisk, vRAM, etc. are typically not an issue.)

For example, the C220M3 TRC#2 works with 8 physical cores or vCPUs.

If the customer needs to deploy the 1000 user CUCM OVA on this host, we are immediately taking up 2 of the 8 vCPUs.  See the below picture for details.


Now, assume we need to add all of the other Cisco UC applications that may reside on this ESXi host like: Unity Connection, Cisco Unified IM & Presence, and Cisco Emergency Responder. These would take up another 2vCPUs each.  At this point, the server is maxed out.


What if the customer wants to add Cisco Unified Contact Center Express, Cisco Unified Enterprise Attendant Console, or Cisco Paging Server? 


In this case, the customer would need to purchase another Cisco UCS server as the C220M3 TRC#2 is completely maxed out. This is why it is important to size out the UCS C Series correctly from the beginning so it has the room to accommodate not only the existing applications but also new future applications.


3)  There is always a decent amount of confusion from customers in terms of what VMWare features are supported by Cisco.


Pasted below is a good table reflecting VMWare features and whether they are supported or are supported but with caveats. For instance, VMWare vMotion is supported but with caveats.

The following applies to any use of vMotion with UC apps:

  • VM must be installed on shared storage (SAN).
  • Source and destination physical servers must be connected to same SAN.
  • Destination physical server must not end up with over-subscribed hardware after the migration. Supported capacity and co-residency rules for UC must be followed before and after the migration.
  • VMware “Long Distance vMotion” (site to site) is not supported.
  • The only supported scenario is a manual move to a different server, e.g. for planned maintenance on the server or VMware software, or during troubleshooting to move software off of a physical server having issues.
  • Use of vMotion for real-time load balancing of live UC VMs is not supported, whether alone or in conjunction with VMware Dynamic Resource Scheduler (DRS) or Dynamic Power Management (DPM).
  • Moving a shut down VM during a maintenance window, i.e. a “cold migration” or “host to host migration”, is not vMotion and is supported.


If the UC app is listed as “Supported with Caveats,” then support is as described below:

  • Migration of UC VMs that are live and processing live traffic is supported, but note that Cisco testing cannot cover every possible operational scenario. Testing has shown there is a slight risk of calls in progress being impacted for a few seconds as the migration occurs, with worst-case result of the affected calls being dropped. If vMotion is suspected as the cause of dropped calls, customers should gather appropriate application logs as well as performance data from VMware vCenter and send to Cisco TAC for analysis. If the UC app is listed as “Partial” support, then support is “maintenance mode only” as described below:
  • “Maintenance mode only” – VMware vMotion by definition operates on live VMs, but the VM running the Cisco UC app must be “live but quiescent”. I.e. in a maintenance window, not in production, not processing live traffic. This is because during the vMotion cutover, the system is paused, which for real-time UC apps creates service interruption which degrade voice quality after the migration for calls in progress.
  • Specifically for Cisco Unified Attendant Consoles, this means the CUxAC VM must not be doing any Hot Swap or taking any active calls, with no active Directory Synchronization in progress.


4)   In certain deployments, it may be required that the customer purchase “VMWare Enterprise Plus Licensing” for each of the physical ESXi hosts.


This only falls into scenarios where the customer wants to do “Quality of Service” at the Nexus 1000V or the VMWare distributed switch level. This is not a requirement from Cisco but should be considered if the customer wants to use the Nexus 1000V functionality inside of the UCS B Series chassis.  However, typically these deployments have sufficient/oversubscribed upstream bandwidth for the peak IOPS and peak network traffic and again not typically required.

It will now be a TAC requirement that all Cisco UC deployments are virtualized for 10.x and above.


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Like what you read? 


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