User's Manual

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Chapter 31 VLAN Configuration
31.1 VLAN Introduction
The virtual local area network (VLAN) is an exchange network which logically groups the devices in LAN.
IEEE issued the IEEE 802.1Q standard in 1999 for realizing the VLAN standard. The VLAN technology
can divide a physical LAN logic address into different broadcast domains. Each VLAN has a group of
devices which have the same demands but the same attributes with those on the physical LAN. Because
it is a logical group, the devices in a same VLAN can be in different physical spaces. The
broadcast/unicast flow within a VLAN cannot be forwarded to other VLANs. Such advantages as flow
control, low device investment, easy network management and high network security, hence, are
obtained.
 Support port-based VLAN
 Support 802.1Q relay mode
 Support the access port
The port-based VLAN is to classify the port into a subset of VLAN supported by the switch.
If the VLAN subnet includes only one VLAN, the port is the access port; if the VLAN subnet
has multiple VLANs, the port is a trunk port; there is a default VLAN among these VLANs,
which is the native VLAN of the port and whose ID is PVID.
 Support VLAN range control
The vlan-allowed parameter is used to control theVLANrange; the vlan-untagged parameter
is used to control the transmission of the untaggedVLANpacket from the port to the
correspondingVLAN.
VLAN planning modes are various such as based on MAC, IP subnet, protocol, or port. As to these VLAN
planning modes, VLAN matchup is conducted by default according to the following order: MAC VLAN, IP-
subnet VLAN, protocol VLAN and at last, port VLAN.
31.2 Dot1Q Tunnel Overview
31.2.1 Preface
Dot1Q Tunnel is a lively name of the tunnel protocol based on 802.1Q encapsulation, which is defined
in IEEE 802.1ad. Its core idea is to encapsulate the VLAN tag of the private network to that of the public
network, and the packets with two layers of tags traverse the backbone network of ISP and finally a
relatively simple L2 VPN tunnel is provided to users. The Dot1Q Tunnel protocol is a simple and
manageable protocol, which is realized through static configuration without signaling support and widely
applied to enterprise networks consisting of L3 switches or small-scale MAN.
The Dot1Q Tunnel attribute of switches just meets this requirement. As a cheap and compact L2 VPN
solution, it is increasingly popular among more and more small-scale users when VPN network is
required. At the inside of carrier’s network, P device need not support the Dot1Q Tunnel function. That
is, traditional L3 switches can meet the requirements fully and protect the investment of the carrier
greatly.
 Enables Dot1Q Tunnel globally.