ES-4024A User’s Guide
Chapter 7 Basic Setting 73
7.4 Introduction to VLANs
A VLAN (Virtual Local Area Network) allows a physical network to be partitioned into
multiple logical networks. Devices on a logical network belong to one group. A device can
belong to more than one group. With VLAN, a device cannot directly talk to or hear from
devices that are not in the same group(s); the traffic must first go through a router.
In MTU (Multi-Tenant Unit) applications, VLAN is vital in providing isolation and security
among the subscribers. When properly configured, VLAN prevents one subscriber from
accessing the network resources of another on the same LAN, thus a user will not see the
printers and hard disks of another user in the same building.
VLAN also increases network performance by limiting broadcasts to a smaller and more
manageable logical broadcast domain. In traditional switched environments, all broadcast
packets go to each and every individual port. With VLAN, all broadcasts are confined to a
specific broadcast domain.
Note: VLAN is unidirectional; it only governs outgoing traffic.
See Chapter 8 on page 79 for information on port-based and 802.1Q tagged VLANs.
7.5 IGMP Snooping
A switch can passively snoop on IGMP Query, Report and Leave (IGMP version 2) packets
transferred between IP multicast routers/switches and IP multicast hosts to learn the IP
multicast group membership. It checks IGMP packets passing through it, picks out the group
registration information, and configures multicasting accordingly. IGMP snooping allows the
switch to learn multicast groups without you having to manually configure them.
The switch forwards multicast traffic destined for multicast groups (that it has learned from
IGMP snooping or that you have manually configured) to ports that are members of that
group. The switch discards multicast traffic destined for multicast groups that it does not
know. IGMP snooping generates no additional network traffic, allowing you to significantly
reduce multicast traffic passing through your switch.
Time Zone Select the time difference between UTC (Universal Time Coordinated, formerly
known as GMT, Greenwich Mean Time) and your time zone from the drop-down list
box.
Apply Click Apply to save the settings.
Cancel Click Cancel to reset the fields to your previous configuration.
Table 9 General Setup (continued)
LABEL DESCRIPTION
