A device that forwards data packets from one local area network (LAN) or wide area network (WAN) to another. Based on routing tables and routing protocols, routers read the network address in each transmitted frame and make a decision on how to send it based on the most expedient route (traffic load, line costs, speed, bad lines, etc.). Routers work at layer 3 in the protocol stack, whereas bridges and switches work at the layer 2.
Routers are used to segment LANs in order to balance traffic within workgroups and to filter traffic for security purposes and policy management. Routers are also used at the edge of the network to connect remote offices. Multiprotocol routers support several protocols such as IP, IPX, AppleTalk and DECnet.
Routers can only route a message that is transmitted by a routable protocol such as IP or IPX. Messages in non-routable protocols, such as NetBIOS and LAT, cannot be routed, but they can be transferred from LAN to LAN via a bridge. Because routers have to inspect the network address in the protocol, they do more processing and add more overhead than a bridge or switch, which both work at the data link (MAC) layer.
Most routers are specialized computers that are optimized for communications; however, router functions can also be implemented by adding routing software to a file server. For example, the NetWare operating system includes routing software that can route from one subnetwork to another if each one is connected to its own network adapter (NIC) in the server. The major router vendors are Cisco Systems and Nortel Networks.
Within an enterprise, routers serve as an internet backbone interconnecting all networks. This architecture strings several routers together via a high-speed LAN topology such as Fast Ethernet or Gigabit Ethernet. Within the global Internet, routers do all the packet switching in the backbones.
Another approach within an enterprise is the collapsed backbone, which uses a single router with a high-speed backplane to connect the subnets, making network management simpler and improving performance.
In older Novell terminology, a router is a network-layer bridge. Routers also used to be called "gateways." For more understanding of how the network layer 3 works within the protocol stack, see TCP/IP abc's. See layer 3 switch, route server, router cluster and routing protocol.
Routers are used to segment LANs in order to balance traffic within workgroups and to filter traffic for security purposes and policy management. Routers are also used at the edge of the network to connect remote offices. Multiprotocol routers support several protocols such as IP, IPX, AppleTalk and DECnet.
Routers can only route a message that is transmitted by a routable protocol such as IP or IPX. Messages in non-routable protocols, such as NetBIOS and LAT, cannot be routed, but they can be transferred from LAN to LAN via a bridge. Because routers have to inspect the network address in the protocol, they do more processing and add more overhead than a bridge or switch, which both work at the data link (MAC) layer.
Most routers are specialized computers that are optimized for communications; however, router functions can also be implemented by adding routing software to a file server. For example, the NetWare operating system includes routing software that can route from one subnetwork to another if each one is connected to its own network adapter (NIC) in the server. The major router vendors are Cisco Systems and Nortel Networks.
Within an enterprise, routers serve as an internet backbone interconnecting all networks. This architecture strings several routers together via a high-speed LAN topology such as Fast Ethernet or Gigabit Ethernet. Within the global Internet, routers do all the packet switching in the backbones.
Another approach within an enterprise is the collapsed backbone, which uses a single router with a high-speed backplane to connect the subnets, making network management simpler and improving performance.
In older Novell terminology, a router is a network-layer bridge. Routers also used to be called "gateways." For more understanding of how the network layer 3 works within the protocol stack, see TCP/IP abc's. See layer 3 switch, route server, router cluster and routing protocol.
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