D-Link xStack DXS-3350SR Installation & User Manual - Port-Based Vlans
DXS-3350SR Gigabit Layer 3 Switch
Port-based VLANs
Port-based VLANs limit traffic that flows into and out of Switch ports. Thus, all devices connected to a port are members of
the VLAN(s) the port belongs to, whether there is a single computer directly connected to a Switch, or an entire department.
On port-based VLANs, NICs do not need to be able to identify 802.1Q tags in packet headers. NICs send and receive
normal Ethernet packets. If the packet's destination lies on the same segment, communications take place using normal
Ethernet protocols. Even though this is always the case, when the destination for a packet lies on another Switch port,
VLAN considerations come into play to decide if the packet gets dropped by the Switch or delivered.
VLAN Segmentation
Take for example a packet that is transmitted by a machine on Port 1 that is a member of VLAN 2. If the destination lies on
another port (found through a normal forwarding table lookup), the Switch then looks to see if the other port (Port 10) is a
member of VLAN 2 (and can therefore receive VLAN 2 packets). If Port 10 is not a member of VLAN 2, then the packet
will be dropped by the Switch and will not reach its destination. If Port 10 is a member of VLAN 2, the packet will go
through. This selective forwarding feature based on VLAN criteria is how VLANs segment networks. The key point being
that Port 1 will only transmit on VLAN 2.
Network resources such as printers and servers however, can be shared across VLANs. This is achieved by setting up
overlapping VLANs. That is ports can belong to more than one VLAN group. For example, setting VLAN 1 members to
ports 1, 2, 3, and 4 and VLAN 2 members to ports 1, 5, 6, and 7. Port 1 belongs to two VLAN groups. Ports 8, 9, and 10 are
not configured to any VLAN group. This means ports 8, 9, and 10 are in the same VLAN group.
VLAN and Trunk Groups
The members of a trunk group have the same VLAN setting. Any VLAN setting on the members of a trunk group will apply
to the other member ports.
NOTE: In order to use VLAN segmentation in conjunction with port trunk groups, you can first
set the port trunk group(s), and then you may configure VLAN settings. If you wish to change
the port trunk grouping with VLANs already in place, you will not need to reconfigure the
VLAN settings after changing the port trunk group settings. VLAN settings will automatically
change in conjunction with the change of the port trunk group settings.
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