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DES-3028 DES-3028P DES-3028G DES-3052 DES-3052P Layer 2 Fast Ethernet Managed Switch
ISM VLAN Settings
In a switching environment, multiple VLANs may exist. Every time a multicast query passes through the Switch, the switch must
forward separate different copies of the data to each VLAN on the system, which, in turn, increases data traffic and may clog up
the traffic path. To lighten the traffic load, multicast VLANs may be incorporated. These multicast VLANs will allow the Switch
to forward this multicast traffic as one copy to recipients of the multicast VLAN, instead of multiple copies.
Regardless of other normal VLANs that are incorporated on the Switch, users may add any ports to the multicast VLAN where
they wish multicast traffic to be sent. Users are to set up a source port, where the multicast traffic is entering the switch, and then
set the ports where the incoming multicast traffic is to be sent. The source port cannot be a recipient port and if configured to do
so, will cause error messages to be produced by the switch. Once properly configured, the stream of multicast data will be relayed
to the receiver ports in a much more timely and reliable fashion.
Restrictions and Provisos
The Multicast VLAN feature of this switch does have some restrictions and limitations, such as:
1. Multicast VLANs can be implemented on edge and non-edge switches.
2. Member ports and source ports can be used in multiple ISM VLANs. But member ports and source ports cannot be the
same port in a specific ISM VLAN.
3. The Multicast VLAN is exclusive with normal 802.1q VLANs, which means that VLAN IDs (VIDs) and VLAN Names
of 802.1q VLANs and ISM VLANs cannot be the same. Once a VID or VLAN Name is chosen for any VLAN, it cannot
be used for any other VLAN.
4. The normal display of configured VLANs will not display configured Multicast VLANs.
5. Once an ISM VLAN is enabled, the corresponding IGMP snooping state of this VLAN will also be enabled. Users
cannot disable the IGMP feature for an enabled ISM VLAN.
6. One IP multicast address cannot be added to multiple ISM VLANs, yet multiple Ranges can be added to one ISM VLAN.
The following windows will allow users to create and configure multicast VLANs for the switch. To view these windows, click
L2 Features > IGMP Snooping > ISM VLAN Settings.
Figure 7- 21. IGMP Snooping Multicast VLAN Table window
The previous window displays the settings for previously created Multicast VLANs. To view the settings for a previously created
multicast VLAN, click the Modify button of the corresponding ISM VLAN you wish to modify. To create a new Multicast VLAN,
click the add new entry link in the top left-hand corner of the screen, which will produce the following window to be configured.
Figure 7- 22. IGMP Snooping Multicast VLAN Settings – Add window
Enter a name for the ISM VLAN into the VLAN Name field and choose a VID between 2 and 4094. Entries in these two fields
must not have been previously configured on the switch or an error message will be prompted to the user. Once these two fields
have been filled, click the Apply button, which will automatically adjust the current window to resemble the following window.
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