Different Network devices
Ethernet hubs are the central device that connects all the PC's in a particular segment. It receives the signals on one of its ports and then re-transmits it to all the other ports except receiving port. UTP cables are used to connect the nodes (computers or printers) to hubs. An active hub receives signals at its ports and strengthens it before passing it on to all the other ports. A passive hub acts just as a simple gateway for the incoming signals and doesn't regenerate the signal before it is passed on to the other ports. An Ethernet hub is available in a variety of sizes and costs, depending on the number of ports that it has. A Smaller hub which has 4, 8, or 12 ports are called workgroup hubs, while a hub with 24 or 32 ports are called high-density hubs. Hubs can be joined together to extend the network segments.
Slightly different from a hub, a switch is also the central device that connects the multiple nodes in a network segment. A switch uses UTP or STP cables. A switch sends the signal only to the main destination node. A switch is an intelligent device that learns the hardware address or Media Access Control (MAC) address of the destinations from the data packets and sends the data packet only to the required node. This improves the efficiency of the network, and means a reduced number of collisions and errors.
Media Access Unit (MAU).
An MAU or also called a Multi-Station Access Unit (MSAU), is used for Token Ring networks as a central device which connects all the nodes in the network segments. This is the equivalent to using hubs or switches in Ethernet networks and the results in giving the network a physical star look, though it still has the same topology of a ring. Multiple MAUs can be connected using the Ring In (RI) and Ring Out (RO) ports in order to extend the network. The RO port of one MAU is connected to the RI port of the second MAU, and more can be connected. The RO port of the last MAU is connected back to the RI port of the first MAU in the network to then complete the ring.
A network bridge is used for two main purposes. This is connecting to LAN segments to form a larger network segment and for dividing a large network segment into smaller network segments. Network switches, and bridges also learn the MAC address of the devices they are connected to, and they forward data packets based on the destination of the MAC address. Most newer bridges can dynamically build the lists of MAC addresses by analyzing data frames. The bridges are called learning bridges due to technology. Most of the functionality of bridges is now included in switches.
Routers are used to connect two or more network segments together. Routers use IP addresses to decide the source and destination of the data packets. Routers receive the data packets, they determine the destination IP address, and then forward the packets to the next hop, which can be either the final destination of the packet, or another router on the path. Routers can be implemented also as a software service or as a dedicated hardware device. A wired or wireless router which is in a home network connects the small network, thanks to the router to the ISP’s network. Routers also communicate to each other using routing protocols. Routers will maintain a list of IP addresses in their routing tables. Routing tables can also be built statically or dynamically.
When static routing is used a network administrator will have to manually configure the routing tables by entering the appropriate routing information. This method is only really used for very small networks.
Dynamic routing makes use of the routers Routing Information Protocol (RIP) or Open Shortest Path First (OSPF) to build, maintain, and to advertise their routing tables. Almost every network now uses dynamic routing.
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