D-Link DES-3326 User Manual - Layer 3-Based Vlans
DES-3326 Layer 3 Fast Ethernet Switch User’s Guide
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Switch Management and Operating Concepts
ingress port is a member of the 802.1Q VLAN, the switch then
determines if the destination port is a member of the 802.1Q
VLAN. If it is not, the packet is dropped. If the destination port is
a member of the 802.1Q VLAN, the packet is forwarded and the
destination port transmits it to its attached network segment.
If the packet is not tagged with VLAN information, the ingress
port will tag the packet with its own PVID as a VID (if the port is a
tagging port). The switch then determines if the destination port is
a member of the same VLAN (has the same VID) as the ingress
port. If it does not, the packet is dropped. If it has the same VID,
the packet is forwarded and the destination port transmits it on its
attached network segment.
This process is referred to as ingress filtering and is used to
conserve bandwidth within the switch by dropping packets that are
not on the same VLAN as the ingress port at the point of reception.
This eliminates the subsequent processing of packets that will just
be dropped by the destination port.
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, but this does not constitute a
‘routing’ function.
The DES-3326 allows an IP subnet to be configured for each
802.1Q VLAN that exists on the switch.
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.