Which of the following allows a single switch to support traffic belonging to several VLANs across the network?

VLANs are used to divide a physical LAN into multiple broadcast domains to isolate services with the aim of improving the security and management of the network. Hosts within a VLAN can directly communicate only with other hosts in the same VLAN and must use a router to communicate with hosts in other VLANs.

In the network shown in Figure 1, two switches are deployed at different locations, for example, on different floors of an office building. Both switches connect to two computers that belong to different enterprises. In this case, the computers can be assigned to different VLANs, achieving isolation of users between enterprises.

Figure 1-1 VLAN networking

A switch identifies packets from different VLANs according to the information contained in its VLAN tags. IEEE 802.1Q adds a 4-byte VLAN tag between the Source/Destination MAC address and Length/Type fields of an Ethernet frame, as shown in Figure 2.

Figure 1-2 VLAN data frame

The VLAN ID (VID) field in a data frame identifies the VLAN to which the data frame belongs (the VLAN in which the data frame can be transmitted). All frames processed on a switch carry VLAN tags, but some devices connected to a switch cannot process tagged frames. To enable communication between the switch and these devices, the switch interfaces must be able to identify whether an Ethernet frame is tagged, and then decide whether to add VLAN tags to or remove VLAN tags from the frames. Hosts in the same VLAN may be connected to different switches, in which case the VLAN spans multiple switches. To enable communication between these hosts, interfaces between switches must be able to identify and send frames of multiple VLANs.

Huawei network devices can be configured with four types of interfaces: access, trunk interface, hybrid interface, and QinQ interface. The four interface types process frames differently and therefore the interface that should be configured depends on what the interface connects to (for example, whether it connects to a host or another switch).

• Access interface: An access interface often connects to a user terminal such as a user host or server that cannot identify VLAN tags, or is used when VLANs do not need to be differentiated. In most cases, access interfaces can only receive and send untagged frames, and can add only a unique VLAN tag to untagged frames.
• Trunk interface: A trunk interface often connects to a switch, a router, an AP, or a voice terminal that can receive and send both tagged and untagged frames. It allows tagged frames from multiple VLANs and untagged frames from only one VLAN to pass through.
• Hybrid interface: A hybrid interface can connect to a user terminal (such as a user host or server) or network device (such as a hub or an unmanaged switch) that cannot identify VLAN tags, and also can connect to a switch, a router, an AP, or a voice terminal that can receive and send both tagged and untagged frames. It allows tagged frames from multiple VLANs to pass through. Whether frames sent out from a hybrid interface are tagged or untagged depends on the VLAN configuration.
• QinQ interface: An 802.1Q-in-802.1Q (QinQ) interface often connects a private network to a public network. It can add an additional 802.1Q tag to a tagged frame. QinQ supports up to 4094 x 4094 VLANs, offering sufficient VLANs required by networks. A QinQ interface is also called a Dot1q-tunnel interface. For details about QinQ, refer to "QinQ Configuration" in the S12700 V200R013C00 Configuration Guide - Ethernet Switching Configuration Guide.

VLANs can be assigned based on interfaces, MAC addresses, policies, IP subnets, and protocols. Table 1 compares different VLAN assignment modes.

Table 1-1 VLAN assignment modes

Interface-based VLAN assignment is the simplest and most widely used of the VLAN assignment modes listed above. The configuration methods vary according to interface type. For details, see Assigning VLANs.

Which of the following features of a switch will allow two switches to pass VLAN network information?

Which of the following is used for moving traffic within individual VLANs?

When a router connects to a switch that supports multiple VLANs it is sometimes called?

On which networking device do you configure VLANs?