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4-4 VLAN Setting
A Virtual LAN (VLAN) is a logical network grouping that limits the broadcast domain. It allows you to isolate network traffic
so only members of the VLAN receive traffic from the same VLAN members. Basically, creating a VLAN from a switch is
logically equivalent of reconnecting a group of network devices to another Layer 2 switch. However, all the network devices
are still plug into the same switch physically.
The Switch supports IEEE 802.1Q (tagged-based) and Port-Base VLAN setting in web management page. In the default
configuration, VLAN support is “No VLAN”.
Port-based VLAN
Port-based VLAN limit traffic that flows into and out of switch ports. Thus, all devices connected to a port are members of
the VLAN(s) the port belongs to, whether there is a single computer directly connected to a switch, or an entire department.
On port-based VLAN.NIC do not need to be able to identify 802.1Q tags in packet headers. NIC send and receive normal
Ethernet packets. If the packet's destination lies on the same segment, communications take place using normal Ethernet
protocols. Even though this is always the case, when the destination for a packet lies on another switch port, VLAN con-
siderations come into play to decide if the packet is dropped by the Switch or delivered.
IEEE 802.1Q VLANs
IEEE 802.1Q (tagged) VLAN are implemented on the Switch. 802.1Q VLAN require tagging, which enables them to span
the entire network (assuming all switches on the network are IEEE 802.1Q-compliant).
VLAN allow a network to be segmented in order to reduce the size of broadcast domains. All packets entering a VLAN wil
only be forwarded to the stations (over IEEE 802.1Q enabled switches) that are members of that VLAN, and this includes
roadcast, multicast and unicast packets from unknown sources.
LAN can also provide a level of security to you ackets between stations
at are members of the VLAN. Any port can be configured as either tagging or untagging. The untagging feature of IEEE
802.1Q VLAN allows VLAN to work with legacy switches that don't recognize VLAN tags in packet headers. The tagging
feature allow 802.1Q-compliant sw single physical connection and allows Span-
nin enabled on all ports and work normally.
An to
wo cy sw he tagging feature allows VLAN to span
multiple 802.1Q-co cal connection and allows Spanning Tree to be enabled on all
ports and work norm
Some relevant term
he act of acket.
- The act of stripping 802.1Q VLAN
80 N Tags
Th rce MAC address.
Th field is equal to
0x et ctets and consists of 3
bits of user priority, 1 bit of Canonical F can be
carried across Ethernet backbo 802.1p. The VID
the VLAN identifier and is us 094 unique VLAN can be
entified.
he tag is inserted into the packet header making the entire packet longer by 4 octets. All of the information originally
ontained in the packet is retained.
l
b
V
th
r network. IEEE 802.1Q VLAN will only deliver p
s VLAN to span multiple
g Tree to be
itches through a
y port can be con
rk with lega
figured as either tagging or untagging. The untagging feature of IEEE 802.1Q VLAN allows VLAN
itches that don’t recognize VLAN tags in packet headers. T
mpliant switches through a single physi
ally.
s:
Tag - T
Untag
putting 802.1Q VLAN information into the header of a p
information out of the packet header.
2.1Q VLA
e figure below sh
eir presence is in
ows the 802.1Q VLAN tag. There are four additional octets inserted after the sou
dicated by a value of 0x8100 in the Ether Type field. When a packet's Ether Type
8100, the pack carries the IEEE 802.1Q/802.1p tag. The tag is contained in the following two o
ormat Identifier (CFI - used for encapsulating Token Ring packets so they
nes), and 12 bits of VLAN ID (VID). The 3 bits of user priority are used by
ed by the 802.1Q standard. Because the VID is 12 bits long, 4is
id
T
c