Virtual switches in ESXi are constructed by and operate in the VMkernel. A virtual switch is not a managed switch and does not provide all the advanced feature of a physical switch. You cannot telnet into a virtual switch to modify settings. No command line interface (CLI) except for the vSphere commands like esxcli.
A virtual switch does operate like a physical switch at Layer 2, maintains MAC address tables, forwards frames to other switch ports based on the MAC address, supports VLAN configurations, can trunk VLANs using the IEEE 802.1q VLAN tags, and can establish port channels. A vDS supports PVLANs provided there is PVLAN support on the upstream physical switches. And like in a physical switch, a vSwitch is configured with a specific number of ports.
Note that there are a number of differences between a physical switch and a vSwitch. A virtual switch does not support the use of dynamic negotiation protocols for establishing 802.1q trunks or port channels, such as Dynamic Trunk Protocol (DTP) or Link Aggregation Control Protocol (LACP). A virtual switch cannot be connected to another virtual switch, thereby eliminating loop configurations. No STP is run on it.
Other differences between a virtual switch and a physical switch:
A virtual switch does operate like a physical switch at Layer 2, maintains MAC address tables, forwards frames to other switch ports based on the MAC address, supports VLAN configurations, can trunk VLANs using the IEEE 802.1q VLAN tags, and can establish port channels. A vDS supports PVLANs provided there is PVLAN support on the upstream physical switches. And like in a physical switch, a vSwitch is configured with a specific number of ports.
Note that there are a number of differences between a physical switch and a vSwitch. A virtual switch does not support the use of dynamic negotiation protocols for establishing 802.1q trunks or port channels, such as Dynamic Trunk Protocol (DTP) or Link Aggregation Control Protocol (LACP). A virtual switch cannot be connected to another virtual switch, thereby eliminating loop configurations. No STP is run on it.
Other differences between a virtual switch and a physical switch:
- Unlike a physical switch, a virtual switch authoritatively knows the MAC addresses of the VMs connected to it, so there is no need to learn MAC addresses from the network.
- Traffic received by a virtual switch on one uplink is never forwarded out another uplink. So no need to run STP.
- A virtual switch does not need to perform Internet Group Management Protocol (IGMP) snooping because it knows the multicast interests of the VMs attached to it.
- A vSwitch does not support the use of dynamic negotiation protocols for establishing 802.1q trunks or port channels, such as DTP (Dynamic Trunking Protocol) or LACP (Link Aggregation Control Protocol). Thus looping, which is a common problem in physical switches, is eliminated and this is a big benefit you see in virtual switches.
As is evident from the above statements, you cannot just use virtual switches in the same manner you would use physical switches. For example, you cannot use a vSwitch as a transit path between two physical switches because traffic received on one uplink of the vSwitch will not be forwarded out through another uplink.
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