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In traditional switched LANs, the physical topology is closely related to the logical topology. • Generally, workstations must be grouped by their physical proximity to a switch. • To communicate among LANs, each segment must have a separate port on the backbone device or a connection to a common backbone. | Chapter 3 Virtual Local Area Networks (VLANs) Part I Virtual Local Area Networks Introducing VLANs Defining VLANs In traditional switched LANs, the physical topology is closely related to the logical topology. Generally, workstations must be grouped by their physical proximity to a switch. To communicate among LANs, each segment must have a separate port on the backbone device or a connection to a common backbone. Separate Broadcast Domains Defining VLANs VLANs provide segmentation based on broadcast domains. VLANs logically segment switched networks based on the functions, project teams, or applications of the organization regardless of the physical location or connections to the network. Communication among VLANs still require a router. BUT, only one physical connection will handle all routing. Separate Broadcast Domains Defining VLANs VLANs are created to provide segmentation services traditionally provided by physical routers in LAN configurations. They address: Scalability . | Chapter 3 Virtual Local Area Networks (VLANs) Part I Virtual Local Area Networks Introducing VLANs Defining VLANs In traditional switched LANs, the physical topology is closely related to the logical topology. Generally, workstations must be grouped by their physical proximity to a switch. To communicate among LANs, each segment must have a separate port on the backbone device or a connection to a common backbone. Separate Broadcast Domains Defining VLANs VLANs provide segmentation based on broadcast domains. VLANs logically segment switched networks based on the functions, project teams, or applications of the organization regardless of the physical location or connections to the network. Communication among VLANs still require a router. BUT, only one physical connection will handle all routing. Separate Broadcast Domains Defining VLANs VLANs are created to provide segmentation services traditionally provided by physical routers in LAN configurations. They address: Scalability Security Network Management Broadcast Filtering Traffic Flow Management Switches may not forward any traffic between VLANs, as this would violate the integrity of the VLAN broadcast domain. Traffic must be routed between VLANs. What Does This Mean? Requirements: - Different department on each floor. - Three different LANs per floor. - Separate networks With routers: Expen$ive! 4 Ports each 3 hubs / floor 10 Broadcast domains - Inefficient traffic flow What Does This Mean? With switches: More scalable Easier to manage 1 Router 3 Broadcast Domains - Efficient traffic flow Defining VLANs A VLAN, then, is a broadcast domain (IP Subnet) created by one or more switches. Defining VLANs The above design shows 3 separate broadcast domains created using one router with 3 ports and 3 switches. The router filters the broadcasts for each LAN. Defining VLANs A better design still creates the 3 separate broadcast domains but only requires 1 switch. The router provides broadcast filtering over a .
