An ESX host's own virtual network interface, named vmk0, vmk1 and so forth. It handles host services like management, vMotion, vSAN and IP storage, as opposed to traffic from VMs.
Also called vmknic.
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Each book explains VMkernel adapter in context, with comparison tables and the common traps.
Terms in this definition
- ESX
VMware's bare-metal hypervisor, installed on each host in a VCF fleet. Up to version 9.0 it was known as ESXi.
- VNet
A private network belonging to a single subscription and region and covering all of that region's availability zones. A VM can only use a VNet located in the same region.
- LIKE
Compares strings with a pattern that can contain the % and _ wildcards. Because it only understands character patterns, searching big volumes of text this way is much slower than using full-text search.
- vMotion
Moves a running VM to another host with no downtime; its storage counterpart, Storage vMotion, relocates the files between datastores instead.
- vSAN
VMware's software-defined storage, which combines local devices across a cluster's ESX hosts into one shared datastore. Available as OSA or ESA, VCF can use it as principal storage.
- General-purpose v1
The older storage account kind (
Storage), which lacks access tiers, Archive and premium file shares and retires on 13 October 2026. Converting to ZRS requires first upgrading to GPv2, a one-way change. - Virtual machines
Infrastructure-as-a-service compute giving complete control of the operating system, making it a fit for lift-and-shift moves and for software relying on OS-level pieces like COM.
Related terms
- Management traffic
Communication between ESX hosts and vCenter, which travels over the management network through a VMkernel adapter. vSphere HA sends its heartbeats this way as well.
- pktcap-uw
Command-line packet capture and tracing for ESX, able to tap the host's networking path at various points such as a physical NIC, a switch port or a VMkernel adapter.
- Restore vDS
DCUI repair option for a host whose vSphere Distributed Switch management networking is wrong: it re-attaches the management adapter to a local ephemeral port with uplinks and VLAN of your choice. Anything else using those uplinks on a VMkernel adapter goes offline, and stateless hosts are not eligible.
- TCP/IP stack
ESX hosts can hold several VMkernel network stacks, each with separate gateway and routes: default, vMotion, provisioning, or custom. Create a VMkernel adapter on the vMotion stack and default-stack adapters stop being usable for vMotion.
- vmkping
Run from the ESX shell, it sends pings sourced from a named VMkernel adapter (-I) to verify VMkernel connectivity. Combine a large packet size (-s) with don't-fragment (-d) to check MTU across the full path.
- vMotion network
Carries live-migration traffic between hosts, each using a VMkernel adapter enabled for vMotion; ideally kept separate from other traffic.
- witness traffic separation
Stretched vSAN deployments can give the witness its own VMkernel adapter for its traffic. That spares the witness host a second interface and removes any need to route between the data network and the witness site.