D-Link DGS-3312SR Product Manual - Vlans
DGS-3312SR Gigabit Layer 3 Switch
Figure 4- 26. Setup Static Multicast Forwarding Table window
The following parameters can be set:
Parameter
Description
VID
The VLAN ID of the VLAN the MAC address below belongs to.
Multicast MAC
Address
The MAC address of the static source of multicast packets. This must be a multicast
MAC address.
Port Settings
Allows the selection of ports that will be members of the static multicast group and
ports that are either forbidden from joining dynamically, or that can join the multicast
group dynamically, using GMRP. The options are None and Egress. None means
there are no restrictions on the port dynamically joining the multicast group. If None is
chosen, then an end station attached to the port can join the multicast group using
GMRP. Egress means the port is a static member of the multicast group.
VLANs
The Switch Web Manager’s VLANs sub-folder is divided into two main windows, 802.1Q Static VLANs and 802.1Q
Port Settings. Each is described after a short overview of VLANs.
VLANs can function somewhat differently in a Layer 3 Switch, that is when the VLANs are Layer 3-based, than if they are
strictly based on Layer 2 information. Since IP Switching among VLANs may be unfamiliar to users who are otherwise
well acquainted with conventional VLANs used in standard Ethernet Switches, some explanation of VLANs used in Layer
3 Switching is presented below. It is essential to fully grasp this difference to take advantage of the improved efficiency of
Layer 3 Switching.
VLANs in Layer 2
In normal 802.1Q VLAN implementation, packets cannot cross VLANs in a Switch that is limited to Layer 2 functions. If
a member of one VLAN wants to connect to another VLAN, the link must be through an external router.
Layer 3-Based VLANs
Layer 3-based VLANs use network-layer addresses (subnet address for TCP/IP) to determine VLAN membership. These
VLANs are based on layer 3 information, however this does not constitute a ‘routing’ function.
The DGS-3312SR and associated DGS-3312SR series Switches allow an IP subnet to be configured for each 802.1Q
VLAN that exists on the Switch. That is, a VLAN can be associated or attached to an IP subnet. This represents an
improvement in performance since it bypasses any routing functions, packets transferred between subnets are reduced to a
“hardware” decision.
Even though a Switch inspects a packet’s IP address to determine VLAN membership, no route calculation is performed,
the RIP protocol is not employed, and packets traversing the Switch are bridged using the Spanning Tree algorithm.
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