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D-Link DES-3225G manual MAC-based Broadcast Domains, 802.1Q VLANs, 802.1Q Vlan Segmentation

Models: DES-3225G

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24-port NWay Ethernet Switch User’s Guide

the utmost flexibility. MAC-based broadcast domains, on the other hand, allow a station to be physically moved yet still belong to the same broadcast domain without having to change and configuration settings.

The untagging feature of IEEE 802.1Q VLANs allows VLANs to work with legacy switches that don’t recognize VLAN tags in packet headers. The tagging feature allows VLANs to span multiple 802.1Q-compliant switches through a single physical connection and allows Spanning Tree to be enabled on all ports and work normally (BPDU packets are not tagged).

MAC-based Broadcast Domains

The Switch supports up to 12 MAC-based broadcast domains, which are by their nature, limited to the Switch itself and the devices connected directly to it.

Since MAC addresses are hard-wired into a station’s network interface card (NIC), MAC-based broadcast domains enable network managers to move a station to a different physical location on the network and have that station automatically retain its broadcast domain membership. This provides the network with a high degree of flexibility since even notebook PC’s can plug into any available port on a network and communicate with the same people and use the same resources that have been allocated to the broadcast domain in which it is a member.

Since MAC-based broadcast domains do not restrict the transmission of known unicast frames to other broadcast domains, they can only be used to define limited broadcast domains. As such, they are best implemented on networks where stations are frequently moving, for example where people using notebook PCs are constantly plugging into different parts of the network.

Setting up MAC-based broadcast domains is a relatively straightforward process. Simply create the broadcast domain by assigning it a name (description) and add MAC addresses for the stations that will be members.

802.1Q VLANs

The Switch supports up to 2000 802.1Q VLANs. 802.1Q 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 802.1Q 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.

There are two key components to understanding 802.1Q VLANs: Port VLAN ID numbers (PVIDs) and VLAN ID numbers (VIDs). Both variables are assigned to a switch port, but there are important differences between them. A user can only assign one PVID to each switch port. The PVID defines which VLAN a packet belongs to when packets need to be forwarded to another switch port or somewhere else on the network. On the other hand, a user can define a port as a member of multiple VLANs (VIDs), allowing the segment connected to it to receive packets from many VLANs on the network. These two variables control a port’s ability to transmit and receive VLAN traffic, and the difference between them provides network segmentation, while still allowing resources to be shared across more than one VLAN.

802.1Q VLAN Segmentation

The following example is helpful in explaining how 802.1Q VLAN segmentation works. Take a packet that is transmitted by a machine on Port 1 that is a member of VLAN 2 and has the Port VLAN ID number 2 (PVID=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, because it’s Port VLAN ID number is 2 (PVID=2).

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Switch Management Concepts

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D-Link DES-3225G manual MAC-based Broadcast Domains, 802.1Q VLANs, 802.1Q Vlan Segmentation
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DES-3225G specifications

The D-Link DES-3225GF and DES-3225G are both robust Ethernet switches designed to meet the networking needs of small to medium-sized enterprises and organizations. These devices are part of D-Link's comprehensive range of unmanaged layer 2 switches, known for their reliability and ease of use.

The DES-3225GF features a total of 25 Ethernet ports, including 24 10/100Base-TX ports and 1 Gigabit SFP slot, while the DES-3225G also comes with 25 ports but includes 24 10/100/1000 Mbps copper ports. Both models support Auto-MDI/MDI-X for seamless connection setup without the need for crossover cables, simplifying the deployment process.

One of the standout features of these switches is their wire-speed performance that enables high-speed data transfers and efficient traffic management. Each port is designed to provide non-blocking switching, which ensures that the bandwidth is fully utilized without any packet loss. The switches support IEEE 802.3x flow control, which helps to manage data flow and prevent overflow during heavy traffic periods.

The DES-3225GF and DES-3225G offer users a simple yet efficient way to expand their network. With a plug-and-play design, they require minimal configuration, allowing for quick integration into existing network infrastructures. These switches are equipped with a durable chassis, ensuring they can withstand the rigors of a busy IT environment.

Both models boast energy-efficient technologies that comply with IEEE 802.3az, which helps in reducing power consumption during periods of inactivity. By detecting link status and adjusting power accordingly, these switches contribute to a more sustainable networking solution.

In terms of form factor, the DES-3225GF and DES-3225G are rack-mounted, making them suitable for integration into standard network cabinets. This design ensures that the devices can be efficiently managed alongside other network equipment.

For management and security, the switches support features such as VLAN tagging and port security, allowing network administrators to segment traffic and protect the network from unauthorized access. With their sturdy build, innovative features, and straightforward implementation, the D-Link DES-3225GF and DES-3225G are ideal choices for organizations looking to enhance their network performance while keeping costs manageable.