Example 3, 1D Trunk Connection to 802.1Q VLAN Network

Figure 4-10 Switch 1 Forwards to 1D Trunk

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Mail Server

Green VLAN

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5.The Mail Server receives the broadcast frame and recognizes it. The Mail Server responds with a unicast frame to User B. This frame crosses the 1D Trunk and is received by Switch 1. Switch 1 classifies the unicast frame as belonging to the Default VLAN (the only membership for the 1D Trunk port).

Switch 1 checks the Filtering Database for the MAC address of User B. User B’s MAC address is located, and Port 2 is identified as User B’s location. The frame is then checked for eligibility and frame format for Port 2. Since Port 2 is a 1Q Trunk port, it is eligible to transmit frames for all VLANs. The frame is tagged and transmitted out Port 2.

The switch also recognizes the MAC address of User B in its Source Address Table, FID 1, and updates that table to contain the MAC address and port combination of the Mail Server.

6.This tagged unicast frame is received by Switch 2. The frame is already tagged as belonging to the Default VLAN, so no classification needs to be done. The switch recognizes User B’s MAC address in its Source Address Table, FID 1, and updates that table to contain the Mail Server’s MAC address and port combination.

The switch checks the Filtering Database for the MAC address of User B. User B’s MAC address is located, and Port 2 is identified as the location of User B. The frame is checked for eligibility and frame format for Port 2. Since Port 2 is a 1Q Trunk port, it is eligible to transmit frames for all VLANs. The frame is tagged and transmitted out port 2.

7.Switch 4 receives the frame on its 1Q Trunk port, Port 4, and examines the frame’s Tag. The frame maintains its Default VLAN classification. The switch also refers to its Source Address Table, FID 1, to see if it can locate an entry for User B. User B is found to be located on Port 1. The switch also updates its Source Address Table, FID 1, with the port and MAC address combination for the Mail Server.

The switch examines the Filtering Database and locates the MAC address entry for User B and Port 1. The frame is then checked for eligibility and frame format for Port 1. As Port 1 is considered eligible to transmit to the Default VLAN, the frame is transmitted out Port 1 without a VLAN Tag.

Examples 4-13

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Enterasys Networks 802.1Q manual Switch 1 Forwards to 1D Trunk

802.1Q specifications

Enterasys Networks, a subsidiary of the Siemens Group, is widely recognized for its comprehensive networking solutions, with a strong emphasis on security, reliability, and performance. One of the key technologies offered by Enterasys is 802.1Q, a critical component of Ethernet networking that establishes standards for VLAN (Virtual Local Area Network) tagging. This technology is essential for enhancing network performance and managing traffic efficiently.

The primary feature of 802.1Q is its ability to create VLANs, which segment a physical network into multiple logical networks. This segmentation improves network security by isolating sensitive data and restricting access to specific users or devices. With VLANs, organizations can reduce broadcast traffic, thereby enhancing overall network efficiency. Different departments within an organization can operate on their own VLAN, ensuring that their traffic is kept separate from others.

One significant technological aspect of 802.1Q is its tagging method. When a frame passes through a switch port configured for IEEE 802.1Q, the switch appends a VLAN tag to the frame. This tag contains important information, such as the VLAN ID, enabling switches and devices throughout the network to identify which VLAN the frame belongs to. This tagging is especially critical in environments where multiple VLANs share the same physical infrastructure.

Another characteristic of Enterasys Networks' implementation of 802.1Q is interoperability with existing network standards and protocols. This means that organizations can implement VLAN tagging without requiring major upgrades or replacements of their switch hardware. Enterasys ensures that its switches are compliant with various industry standards, making it easier for enterprises to integrate these solutions into their existing network settings.

Security is another vital feature of Enterasys Networks’ 802.1Q offering. By leveraging VLANs, organizations can enforce stricter access controls and policies, reducing the risk of unauthorized access to sensitive network segments. This is particularly beneficial for industries with stringent compliance requirements, such as finance and healthcare.

In summary, Enterasys Networks' 802.1Q technology plays a pivotal role in modern networking by facilitating VLAN creation, enabling efficient traffic management, ensuring interoperability, and bolstering network security. As organizations increasingly rely on connected devices and data-driven processes, technologies like 802.1Q are essential for building robust, scalable, and secure networking environments.