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This page will discuss the advantages of LAN segmentation and will describe LAN segmentation using bridges, switches, and routers. Also described will be the benefits of using each of these three internetworking devices.Describe the advantages of LAN segmentation
When separate networks are needed or if a network has reached its physical limitations, segmentation is used. Segmenting a LAN can extend the network, reduce congestion, isolate network problems, and improve security.
The term bridging refers to a technology in which a device (known as a bridge) connects two or more LAN segments. A bridge transmits datagrams from one segment to their destinations on other segments.
Bridges are capable of filtering frames based on any Layer 2 fields. A bridge, for example, can be programmed to reject (not forward) all frames sourced from a particular network. Because link-layer information often includes a reference to an upper-layer protocol, bridges usually can filter on this parameter. Furthermore, filters can be helpful in dealing with unnecessary broadcast and multicast packets. Because only a certain percentage of traffic is forwarded, a bridge or switch diminishes the traffic experienced by devices on all connected segments. The bridge or switch will act as a firewall for some potentially damaging network errors, and both accommodate communication between a larger number of devices than would be supported on any single LAN connected to the bridge.Describe LAN segmentation using routers.
Because routers use Layer 3 addresses, which typically have structure, routers can use techniques (such as address summarization) to build networks that maintain performance and responsiveness as they grow in size. Segments are interconnected by routers to enable communication between LANs while blocking other types of traffic. Routers also allow for the interconnection of disparate LAN and WAN technologies while also implementing broadcast filters and logical firewalls. In general, if you need advanced internetworking services, such as broadcast firewalling and communication between dissimilar LANs, routers are necessary.Describe LAN segmentation using switches.
Switches are data link layer devices that, like bridges, enable multiple physical LAN segments to be interconnected into a single larger network. Similar to bridges, switches forward and flood traffic based on MAC addresses. Because switching is performed in hardware instead of in software, however, it is significantly faster. Switches use either store-and-forward switching or cut-through switching when forwarding traffic.
Segmenting shared-media LANs divides the users into two or more separate LAN segments, reducing the number of users contending for bandwidth. LAN switching technology, which builds upon this trend, employs microsegmentation, which further segments the LAN to fewer users and ultimately to a single user with a dedicated LAN segment. Each switch port provides a dedicated, 10MB Ethernet segment. Segments are interconnected by internetworking devices that enable communication between LANs while blocking other types of traffic. Switches have the intelligence to monitor traffic and compile address tables, which then allows them to forward packets directly to specific ports in the LAN. Switches also usually provide nonblocking service, which allows multiple conversations (traffic between two ports) to occur simultaneously.
LAN switches can be used to segment networks into logically defined virtual workgroups (VLANs). This logical segmentation, commonly referred to as VLAN communication, offers a fundamental change in how LANs are designed, administered, and managed. Logical segmentation provides substantial benefits in LAN administration, security, and management of network broadcast across the enterprise.
Superior throughput performance, higher port density, lower per-port cost, and greater flexibility have contributed to the emergence of switches as replacement technology for bridges and as complements to routing technology.Describe the benefits of network segmentation with bridges.
Transparent bridges successfully isolate intrasegment traffic, thereby reducing the traffic seen on each individual segment. This usually improves network response times, as seen by the user.
Routers offer the following benefits in LAN segmentation:
Layer 2 switches offer some or all of the following benefits:
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