Default Vlans; Vlan Segmentation - D-Link DXS-3326GSR Manual

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.

Default VLANs

The Switch initially configures one VLAN, VID = 1, called "default." The factory default setting assigns all ports on the
Switch to the "default." As new VLANs are configured in Port-based mode, their respective member ports are removed
from the "default."
Packets cannot cross VLANs. If a member of one VLAN wants to connect to another VLAN, the link must be through an
external router.
An example is presented below:
VLAN Name
System (default)
Engineering
Marketing
Finance
Sales
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.
DXS-3326GSR Gigabit Layer 3 Switch
NOTE: If no VLANs are configured on the Switch, then all packets will be
forwarded to any destination port. Packets with unknown source
addresses will be flooded to all ports. Broadcast and multicast packets will
also be flooded to all ports.
VID
1
2
3
4
5
Table 6- 2. VLAN Example - Assigned Ports
Switch Ports
5, 6, 7, 8, 21, 22, 23, 24
9, 10, 11, 12
13, 14, 15, 16
17, 18, 19, 20
1, 2, 3, 4
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