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Chapter 3 General Management of the Switch 3-39
3.3 Configuring Global Network Protocols
This section describes how to configure global switch settings for virtual LANs,
multicast service, Spanning Tree Algorithm, handling data based on specific class-of-
service requirements, and displaying the address table or setting static addresses.
3.3.1 VLAN Configuration
In conventional networks with routers, broadcast traffic is split up into separate
domains. Switches do not inherently support broadcast domains. This can lead to
broadcast storms in large networks that handle traffic such as IPX or NetBEUI. By
using IEEE 802.1Q-compliant VLANs, you can organize any group of network nodes
into separate broadcast domains, thus confining broadcast traffic to the originating
group. This also provides a more secure and efficient network environment.
An IEEE 802.1Q VLAN is a group of ports that can be located anywhere in the
network, but communicate as though they belong to the same physical segment.
VLANs help to simplify network management by allowing you to move devices to a
new VLAN without having to change any physical connections. VLANs can be
organized to reflect departmental groups (such as Marketing or R&D), usage groups
(such as e-mail), or multicast groups (used for multimedia applications such as
videoconferencing).
VLANs provide greater network efficiency by reducing broadcast traffic and enable
you to make network changes without having physically change network
connections. VLANs inherently provide a high level of network security since traffic
must pass through a configured Layer-3 link to reach a different VLAN.
This switch supports the following VLAN features:
■ Up to 255 VLANs based on the IEEE 802.1Q standard
■ Distributed VLAN learning across multiple switches using explicit or implicit
tagging
■ Port overlapping, allowing a port to participate in multiple VLANs
■ End stations can belong to multiple VLANs
■ Passing traffic between VLAN-aware and VLAN-unaware devices
■ Priority tagging
Before enabling VLANs for the switch, you must first assign each port to the VLAN
group(s) in which it will participate. By default all ports are assigned to VLAN 1 as
untagged ports. Add a port as a tagged port if you want it to carry traffic for one or
more VLANs, and any intermediate network devices or the host at the other end of