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460T Ch2.p65
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2
Using the Express 460T Switch
IEEE 802.1Q (tag)-based VLANs
The third type of VLAN supported by the Express 460T switch is based on
the IEEE 802.1Q specification. The specification provides a uniform way
for creating VLANs within a network and allows the creation of a VLAN
that can also span across the network. Until recently, VLAN implementation
has been vendor specific so it was not possible to create a VLAN across
devices from different vendors.
The 802.1Q VLAN works by using a tag added to the Ethernet frames. The
tag contains a VLAN Identifier (VID) that identifies the frame as belonging
to a specific VLAN. These tags allow switches that support the 802.1Q
specification to segregate traffic between devices and communicate a
device's VLAN association across switches.
VLAN 1:
Engineering
VLAN 1 computers
can't see VLAN 2
computers
There are multiple advantages to implementing 802.1Q VLANs. First, it
helps to contain broadcast and multicast traffic across the switch thus
improving performance. Second, ports can belong to more than one VLAN.
Third, VLANs can span multiple switches that support the 802.1Q
specification. Finally, it can provide security and improve performance by
logically isolating users and grouping them together. The Express 460T
switch supports up to 256 tag-based VLANs.
A logical grouping may be mapped to a work group. For example, you can
create a VLAN that groups all the users from the engineering department
into one VLAN. A benefit of this logical grouping is that it can improve
performance by cutting down traffic that belongs to a different logical group
(e.g. marketing), improve security (engineering can't see marketing), and
ease moves since the user doesn't have to be physically located in the same
group to participate in the VLAN.
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Module A
®
Port 1
Port 2
Intel
Express 460T Standalone Switch
Status
Link\Act\Coll
Link\Act\Coll
MDI
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
MDI-X
4/19/00, 4:10 PM
Status
Left
22
23
24
Link = Solid Green
Activity = Blinking Green
Collision = Blinking Orange
Right
10Mbps = Solid Orange
100Mbps = Off
VLAN 2:
Manufacturing
Server and printer
are members of both
VLANs
19
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