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Bridges and switches are data communication devices that operates at Layer 2 of OSI reference model?. Bridge can connect multiple LAN? segment together to form a bigger LAN. Station configured in different LAN can communicate directly at Layer 2 level with each other.
switch operates at the data link layer, and are transparent to higher layer protocols, transferring frames between the data link layers of the networks to which it is attached. A switch can store and forward frames, it can examine and discard or admit frames according to some filtering criteria. The switch can also examine the address fields of the frames and forward the frames based on knowledge of which network contains the station with an address matching the frames destination address. In this way, the switch can act as an intelligent filtering device, redirecting or blocking the movement of frames between networks.
Switch can also divide one physical LAN into multiple Virtual LANs (VLANs). Stations connected to each other on the same extended LAN can be grouped in separate VLANs, so that a station in one VLAN can communicate directly with other stations in the same VLAN, but must go through higher layer routing protocols to communicate with stations in other VLANs.
The switch can be used to:
- Increase the physical extent and/or the maximum number of stations on a LAN.
- LANs are limited in their physical extent by the signal distortion and propagation delay characteristics of the media. The switch overcomes this limitation by receiving a frame on one LAN and then retransmitting the frame on another LAN, using the normal access methods for each LAN. The physical characteristics of the LAN media also place a practical limit on the number of stations that can be connected to a single LAN segment. The switch overcomes this limitation by joining LAN segments together to form an extended LAN capable of supporting more stations than either of the individual LANs.
- Connect LANs that have a common data link layer protocol but different physical media, for example, Ethernet 10BASET, 100BASET, and 10BASEF.
- Increase the availability of LANs by allowing multiple redundant paths to be physically configured, and selected dynamically, using the STP(Spanning Tree Protocol).
- Reduce the load on a LAN or increase the effective bandwidth of a LAN, by filtering traffic.
- Prioritise the transmission of data with high Quality of Service requirements.
Switch Ports
Each port in a switch is associated with one of the physical interfaces on the switch. Each port is uniquely identified by a port number. The switch supports a number of features at the physical level that allows it to be connected in a variety of physical networks. This physical layer (Layer 1) versatility includes:
- Enabling and disabling Ethernet ports.
- Autonegotiation of port speed and duplex mode for all 10/100 Ethernet ports and copper gigabit ports.
- Manual setting of port speed and duplex mode for all 10/100 Ethernet ports and copper gigabit ports.
- Port trunking or Link aggregationLACP.
- Port mirroring.
Categories: Broadband
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