By default, a virtual NIC on a guest VM operates in access mode. In this mode, the virtual NIC can send and receive traffic only over its own VLAN, which is the VLAN of the virtual network to which it is connected. If restricted to using access mode interfaces, a VM running an application on multiple VLANs (such as a firewall application) must use multiple virtual NICs—one for each VLAN. Instead of configuring multiple virtual NICs in access mode, you can configure a single virtual NIC on the VM to operate in trunk mode. A virtual NIC in trunk mode can send and receive traffic over any number of VLANs in addition to its own VLAN. You can trunk specific VLANs or trunk all VLANs. You can also convert a virtual NIC from the trunk mode to the access mode, in which case the virtual NIC reverts to sending and receiving traffic only over its own VLAN.