vNIC

In the Ultra Transcenders books

NCP-MCI-7.5

Each book explains vNIC in context, with comparison tables and the common traps.

Terms in this definition

• Subnet

  A segment of a VNet's address space from which resources receive private IPs. Azure holds back five addresses per subnet (the first four and the last), leaving 251 usable in a /24 and three in a /29, the smallest IPv4 subnet.

Related terms

• ACPI

  A standard that lets a hypervisor tell a guest operating system about power and device events. AHV's vm.reboot sends one of these events, and removing a vNIC finishes only once the guest answers the request.

• AHV Traffic Mirroring

  Sends a copy of the packets on chosen AHV host ports to the vNIC of a receiving VM, so they can be inspected for security, troubleshooting or compliance reasons.

• DFW

  Distributed firewall. Stateful rules from NSX (vDefend) are enforced right at each virtual NIC inside the hypervisor, giving micro-segmentation between workloads. Gateway firewalls on Tier-0/1 are a separate thing.

• Enhanced VMXNET

  Virtual NIC whose lack of support on a destination ESX version can prevent migrating a VM there.

• Gateway Firewall

  Stateful NSX filtering at Tier-0 or Tier-1 gateways for north-south flows crossing them. The distributed firewall handles east-west flows at each virtual NIC instead.

• MAC learning

  Off unless switched on, this distributed port group policy lets one vNIC present many source MAC addresses (nested ESX is a typical case), with up to 4096 learnt per port by default and unknown unicast frames flooded. VMware documents it as a better option than promiscuous mode.

• VLAN Basic Subnet

  Can later be migrated to a VLAN Subnet, and lets a vNIC change Basic subnets with no need to rebuild it. Prism Central's Create Subnet workflow offers this type by default.