1-4
z Independent VLAN learning (IVL), where the switch maintains an independent MAC address
forwarding table for each VLAN. The source MAC address of a packet received in a VLAN on a port
is recorded to the MAC address forwarding table of this VLAN only, and packets received in a
VLAN are forwarded according to the MAC address forwarding table for the VLAN.
Currently, the Switch 4200G series Ethernet switches adopt the IVL mode only. For more information
about the MAC address forwarding table, refer to the “MAC Address Forwarding Table Management”
part of the manual.
VLAN Interface
Hosts in different VLANs cannot communicate with each other directly unless routers or Layer 3
switches are used to do Layer 3 forwarding. The Switch 4200G series Ethernet switches support VLAN
interfaces configuration to forward packets in Layer 3.
VLAN interface is a virtual interface in Layer 3 mode, used to realize the layer 3 communication
between different VLANs, and does not exist on a switch as a physical entity. Each VLAN has a VLAN
interface, which can forward packets of the local VLAN to the destination IP addresses at the network
layer. Normally, since VLANs can isolate broadcast domains, each VLAN corresponds to an IP network
segment. And a VLAN interface serves as the gateway of the segment to forward packets in Layer 3
based on IP addresses.
VLAN Classification
Depending on how VLANs are established, VLANs fall into the following six categories.
z Port-based VLANs
z MAC address-based VLANs
z Protocol-based VLANs
z IP-subnet-based VLANs
z Policy-based VLANs
z Other types
At present, the Switch 4200G series switches support the port-based VLANs.
Port-Based VLAN
Port-based VLAN technology introduces the simplest way to classify VLANs. You can assign the ports
on the device to different VLANs. Thus packets received on a port will be transmitted through the
corresponding VLAN only, so as to isolate hosts to different broadcast domains and divide them into
different virtual workgroups.
Ports on Ethernet switches have the three link types: access, trunk, and hybrid. For the three types of
ports, the process of being added into a VLAN and the way of forwarding packets are different.
Port-based VLANs are easy to implement and manage and applicable to hosts with relatively fixed
positions.
Link Types of Ethernet Ports
You can configure the link type of a port as access, trunk, or hybrid. The three link types use different
VLAN tag handling methods. When configuring the link type of a port, note that:
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