Standard vSwitch Port Scale

Reading through the documentation for vSphere 5.5 something caught my eye…thought I’d share:

“For hosts running ESXi 5.1 and earlier, you can configure the number of ports that are available on a standard switch as the requirements of your environment change. Each virtual switch on hosts running ESXi 5.1 and earlier provides a finite number of ports through which virtual machines and network services can reach one or more networks. You have to increase or decrease the number of ports manually according to your deployment requirements.

NOTE Increasing the port number of a switch leads to reserving and consuming more resources on the host.If some ports are not occupied, host resources that might be necessary for other operations remain locked and unused.

To ensure efficient use of host resources on hosts running ESXi 5.5, the ports of virtual switches are dynamically scaled up and down. A switch on such a host can expand up to the maximum number of ports supported on the host. The port limit is determined based on the maximum number of virtual machines that the host can handle.”

I learn something new every day!!

Comparing Virtual Network Adapter Types


Emulated version of the AMD 79C970 PCnet32. Older 10 Mbps NIC with drivers available in most 32-bit guest OSes except Windows Vista and newer.


Paravirtualized adapter, optimized for performance in virtual machines. VMware Tools is required for VMXNET driver.


Emulated version of the Intel 82545EM 1Gbps NIC. Available in Linux versions 2.4.19 and later, Windows XP Professional x64 Edition and later, and Windows Server 2003 (32-bit) and later. No jumbo frames support prior to ESX/ESXi 4.1.


Emulated version of the Intel 82574 1Gbps NIC. Only available on hardware version 8 or newer VMs in vSphere 5.x. Default vNIC for Windows 8 and newer Windows guest OSes. Not available for Linux OSes from the UI.


Paravirtualized adapter, providing more features than VMXNET, such as hardware offloads and jumbo frames. Limited guest OS support for VMs on ESX/ESXi 3.5 and later.


Paravirtualized adapter, unrelated to previous VMXNET adapters. Offers all VMXNET2 features as well as multiqueue support, MSI/MSI-X interrupt delivery, and IPv6 offloads. Supported only for hardware version 7 or later with limited guest OS support.

The vmxnet adapters are paravirtualized device drivers for virtual networking. A paravirtualized driver improves performance since it shares a ring buffer between the virtual machine and the VMkernel. This uses zero-copy, reducing internal copy operations between buffers, which saves CPU cycles. The vmxnet adapters can offload TCP checksum calculations and TCP segmentation to the network hardware instead of using the virtual machine monitor’s CPU resources.

net-dvs Command

In order to view more information about the distributed switch configuration, use the net-dvs command. This is only available in the local shell. Notice that it specifies information like the UUID of the distributed switch and the name. We can also see information regarding Private VLANs if we have those set up.

If we keep scrolling down, we can see the MTU and CDP information for the distributed switch. Notice that we can set up LLDP for a distributed switch. Next we see information regarding the port groups and how they are configured, we see VLAN and security policy information here. At the bottom we see some stuff on a network resource pool if we have network i/o control enabled and are using this feature.

The last section we see on the net-dvs output we see is some information that is very useful during the troubleshooting process. We can see whether or not packets are being dropped and we can see from the amount of traffic going in and out and decide on whether we need to traffic shape.

esxtop Network View

The last post discussed navigating esxtop, now let’s get into each view a little bit more.

There are several network counters that are default when you go to the networking view, here’s a brief overview of each:

PKTTX/s – # of packets transmitted per second

MbTX/s – MegaBits transmitted per second

PKTRX/s – # of packets received per second

MbRX/s –  MegaBits received per second

%DRPTX – percentage of transmit packets dropped

%DRPRX – percentage of receive packets dropped

A major indicator of potential network performance issues is dropped packets. This can be indicative of a physical device failing, queue congestion, bandwidth issues, etc.

Something else to check when having network issues is high CPU usage, the CPU Ready Time counter (%RDY) can be beneficial when diagnosing CPU issues.

If you are having these issues in your environment, consider using jumbo frames, taking advance of hardware features provided by the NIC like TSO (TCP Segmentation Offload) and TCO (TCP Checksum Offload)

Also, make sure to check out physical network trunks, interswitch links, etc for overloaded pipes.

Consider: moving the VM with high network demand to another switch, adding more uplinks to a virtual switch and check for which vNIC driver is being used.

Organizational Networks in vCloud Director 5.1

Organization Network

An organization network provides network services to one particular organization, whereas an external network is created at the provider level and supplies connectivity to multiple organizations. There are three options when creating organization networks: internal, NAT-connected, and direct-connected. An organization administrator cannot create an organization network due to the configuration of external IPs; only a system administrator can configure this.


An organization can be set up so that it does not have a connection to the Internet or a connection to any other external network, just an internal connection. An internal-only network could be set up for groups of test virtual machines; a virtual machine can be configured with multiple network interfaces so that it has a connection to the internal network as well as one of the other two types. With an internal organization network, vApps can connect, but there is no traffic outside the organization.

Network Address Translation (NAT)-Connected

Network Address Translation (NAT)-connected, sometimes called a “routed network,” can be connected to the external network through a vShield Edge device. The vShield Edge device provides port-forwarding services, NAT, DNS forwarding, and DHCP services to the network; the vShield Edge device gets provisioned automatically
by vCloud Director as needed. A NAT connection allows for virtual machines to communicate with each other while only having one IP seen from the Internet. Another use of NAT is to fence, which includes two sets of IP addresses: external and internal. Fencing allows for several vApps to utilize the same internal IP addresses and extremely useful for test environments.

Direct Communication

The last option for an organization network is a direct connection. The organization would use an external net- work to connect to external systems, including the Internet. Using this method, a user can connect directly to a virtual machine using remote desktop or even SSH. If a vApp configured for a direct connection then the vApp’s IP addresses must be statically assigned or a DHCP server must be connected to the external providing the vApp with those IP addresses.

For further reading, check out my vCloud Director 5.1 Networking Concepts white paper!

vCloud Director 5.1 Networking Concepts (Introduction)

A VMware vCloud is made up of one or more vCloud Director servers that are integrated with underlying vSphere components. The vCloud is a new abstraction layer above vCenter Server consuming the resources that vCenter manages; this allows a user to self-provision virtual environments utilizing memory, compute, storage, and networking resources. Cloud computing has become a vague, arbitrary phrase, but there are six characteris- tics that define exactly what a cloud should consist of

  • self-service
  • elasticity
  • pay as you go
  • multi-tenancy
  • resource pooling
  • ubiquitous access

A private cloud is an infrastructure whose resources are only used internally. A public cloud is an infrastructure made available to external customers for a price. A hybrid cloud combines two or more clouds with some kind of standardized technology, like VMware vCloud Connector, while each cloud maintains its own unique identity.

The foundation of the vCloud centers on the networking configuration. Networking occurs over three different layers: external, organization, and vApp; it is imperative to properly configure and manage these networks so that the vCloud can be consumed. Think of vCloud networking as an onion that will be peeled back to reveal each layer, starting with the organization’s networks that are created by an administrator with the system administrator role in vCloud Director. A system administrator is the highest role within the vCloud.

For further reading, check out my vCloud Director 5.1 Networking Concepts white paper!

External Networks in vCloud Director 5.1

The first object that is created within vCloud Director is the External Network. An External Network provides the connection from the cloud to the outside world, allowing inter-Cloud connections and is port group based. Even though this connection is called the external connection, an Internet connection is not actually required; this can be set up to provide a connection to several different internal entities, like ESXi hosts, without an actual route

to the Internet. Since this connection is port group-based, then the port group needs to exist prior to attempting to establish the connection. The port group can be defined on a standard vSwitch, a distributed vSwitch, or on a Nexus 1000V. Organization virtual datacenters can use the external networks to provide Internet connectivity to the organizations and the virtual machines that reside within a vApp, given that the vApp network is configured for that. By creating an external network, vCloud Director is effectively configured to send all external traffic using the port group(s) selected. Should there be multiple external networks created then be sure to separate them by using VLANs. Only someone with the system administrator role within the vCloud can create and man- age external networks.

For further reading, check out my vCloud Director 5.1 Networking Concepts white paper!