Determining the Number of VMware Servers Needed

How Many VMware Servers Do I Need?

If you are using the topologies designed to support Cisco Networking Academy® content, please refer to the table below. The number of VMware servers and memory requirements vary based on the lab topologies and number of pods you plan to implement.

Step 1. Carefully study the lab topologies and determine the number of virtual switches and virtual machines required by each pod. The requirements for each pod shown below assume that you are implementing all PCs supported by the pod.

Please Note: The topologies listed here are the only ones from the collection of topologies designed for Cisco Networking Academy content that support virtual machines.

Topology Maximum Virtual Switches (VMnet) Maximum Virtual Machines
MAP 3 3
NFP 5 required, 2 optional 5 required, 2 optional
CRP 4 5
CRP 4 4
LSP 3 4
NSP 5 7
BRPv2 3 4
BSPv2 3 3
SRP 3 5
SRP 5 7

  VMware Server (Windows) supports 10 virtual switches per server. This is a hard limit. The number of virtual switches (VMnet) required for your lab topologies could effectively limit the number of virtual machines you can implement on a single VMware server. Please consider this when evaluating your VMware server hardware requirements. You do not want to purchase a very high-end system capable of running 20 virtual machines, only to realize later that virtual switch requirements for your topologies will limit you to a smaller number!

This limitation is specific to VMware Server. The virtual switch limit is not a factor if you are using ESXi.

We recommend no more than 10 to 12 virtual machines per server. Each virtual machine uses CPU cycles and memory on the server. As a simple rule of thumb, divide the processor clock speed by the number of virtual machines to determine the speed of each virtual machine in a heavily loaded environment (i.e. all pods are running at the same time and users are working on the PCs). For example, a 3GHz processor could run 10 virtual machines at 300MHz each. This does not account for overhead on the host operating system.

Step 2. Add up the number of virtual switches and virtual machines used by each pod you are implementing. For example:

Pod Name Type Virtual Switches Virtual Machines
POD 1 Basic Router Pod Version 2 3 4
POD 2 Basic Router Pod Version 2 3 4
POD 3 Basic Router Pod Version 2 3 4
POD 4 Basic Router Pod Version 1 0 (n/a) 0 (n/a)
POD 5 Basic Switch Pod Version 2 3 3
POD 6 Network Security Pod (2.0) 5 7
Total   17 22

Step 3. Assign each pod that supports PCs to a VMware server.

In step, we determined that 17 virtual switches are required. Since you can have up 10 virtual switches per server, you would need at least 2 VMware servers for this implementation. Server 1 could accommodate POD1, POD2, and POD3. Server 2 could accommodate POD5 and POD6. Note, POD4 does not support PCs and uses no VMware resources.


VMware Server #1

Pod Name Type Virtual Switches Virtual Machines
POD 1 Basic Router Pod Version 2 3 4
POD 2 Basic Router Pod Version 2 3 4
POD 3 Basic Router Pod Version 2 3 4
Total   9 12

VMware Server #2

Pod Name Type Virtual Switches Virtual Machines
POD 5 Basic Switch Pod Version 2 3 3
POD 6 Network Security Pod (2.0) 5 7
Total   8 10

Step 4. Based on the pod type and curriculum requirements, determine which guest operating system you will use on each virtual machine. Tabulate the operating system and memory requirements for the host operating system and virtual machines. You should allocate the same amount of memory as you would if standing up a real PC. The following would represent typical choices for VMware Server 1 in the previous example.


VMware Server #1

Pod PC Name Operating System Memory (MB)
n/a VMware Host O/S Windows Server 2003 512
POD 1 PC1a Windows XP 128
POD 1 PC1b Windows XP 128
POD 1 PC2 Windows XP 128
POD 1 PC3 Windows XP 128
POD 2 PC1a Windows XP 128
POD 2 PC1b Windows XP 128
POD 2 PC2 Windows XP 128
POD 2 PC3 Windows XP 128
POD 3 PC1a Windows XP 128
POD 3 PC1b Windows XP 128
POD 3 PC2 Windows XP 128
POD 3 PC3 Windows XP 128
Total     2048 (2GB)

VMware Server #2

Pod PC Name Operating System Memory (MB)
n/a VMware Host O/S Windows Server 2003 512
POD 5 PC1a Windows XP 128
POD 5 PC2 Windows XP 128
POD 5 PC3 Windows XP 128
POD 6 PC1 Windows XP 128
POD 6 IS1 Windows 2000 Server 256
POD 6 DMZ1 Linux 64
POD 6 BB Windows 2000 Server 256
POD 6 PC2 Windows XP 128
POD 6 IS2 Windows 2000 Server 256
POD 6 DMZ2 Linux 64
Total     2048 (2GB)

  To utilize all available virtual switches on a VMware server, it is possible to split virtual switches and machines in a single pod across two different VMware servers. You should be very familiar with the remote PC and virtual switch layout for each pod before attempting this.

Step 5. Translate the requirements from steps 1 through 4 into an itemized list for each server.

The two VMware servers in the previous examples would require the following items.


VMware Server #1

Quantity Item Role
1 Intel Pentium 4 Server
  • 3.0GHz or higher
  • 2048MB RAM (2GB)
  • 2 x 80GB Hard Disks with RAID1 support
  • Dual (2) Intel Network Interfaces with 802.1q VLAN tag support
 server hardware
1 VMware Server for Windows 1.0.1 - 1.0.7 virtual machine software
1 Windows 2003 Server - Standard Edition host operating system
12 Windows XP (Home or Pro) guest operating systems

VMware Server #2

Quantity Item Role
1 Intel Pentium 3 Server
  • 3.0GHz or higher
  • 2048MB RAM (2GB)
  • 2 x 80GB Hard Disks with RAID1 support
  • Dual (2) Intel Network Interfaces with 802.1q VLAN tag support
 server hardware
1 VMware Server for Windows 1.0.1 - 1.0.7 virtual machine software
1 Windows 2003 Server - Standard Edition host operating system
5 Windows XP (Home or Pro) guest operating systems
3 Windows 2000 Server guest operating systems
2 Linux guest operating systems