Vlan Interface; Vlan Classification; Port-Based Vlan; Link Types Of Ethernet Ports - 3Com 4500 Configuration Manual

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, Switch 4500 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 4500 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.
Port-based VLANs
MAC address-based VLANs
Protocol-based VLANs
IP-subnet-based VLANs
Policy-based VLANs
Other types
At present, the Switch 4500 series switches support the port-based VLANs.

Port-Based VLAN

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:
An access port can belong to only one VLAN. Usually, ports directly connected to PCs are
configured as access ports.
A trunk port can carry multiple VLANs to receive and send traffic for them. Except traffic of the
default VLAN, traffic passes through a trunk port will be VLAN tagged. Usually, ports connecting
network devices are configured as trunk ports to allow members of the same VLAN to
communicate with each other across multiple network devices.
Like a trunk port, a hybrid port can carry multiple VLANs to receive and send traffic for them. Unlike
a trunk port, a hybrid port allows traffic of all VLANs to pass through VLAN untagged. You can
configure a port connected to a network device or user terminal as a hybrid port for access link
connectivity or trunk connectivity.
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