D-Link DES-3250TG User Manual page 47

DES-3250TG Layer 2 Fast Ethernet Switch User's Guide
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.
The "Default" VLAN
The switch initially configures one VLAN, VID = 1, called the
"default" VLAN. The factory default setting assigns all ports on
the switch to the "default" VLAN.
Packets cannot cross VLANs. If a member of one VLAN wants to
connect to another VLAN, the link must be through an external
router.
If no VLANs are configured on the switch, then all packets will
be forwarded to any destination port. Packets with unknown
destination addresses will be flooded to all ports. Broadcast
and multicast packets will also be flooded to all ports.
VLANs
VLANs use network-layer addresses (subnet address for
TCP/IP) to determine VLAN membership. These VLANs are
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