Router is a hardware device that manages the route selection for packet data. Routers are used to connect two different networks. Each network may have been implemented independently and include stations with same address. If a LAN message is intended for another network, the router accepts it. Each individual router understands the entire internet topology. After a router determines the best route for a message, it is passed along the route and the address of the route.
External routers require a micro, two or more network interface cards, and router software. They support a local interface, remote interface and protocols; and can handle concurrent communication among different LAN access methods, such as Ethernet, token ring, and fiber distributed data interface. However, only nodes that use the same protocol can be linked. Router use the network layer address, they can determine the best internet work path between any two nodes. This might be a function of the cheapest, most cost-effective, least congested, highest data rate, least number of hopes between and nodes, or some combination of these factors.
The path between routers is decided by inter router communications protocols. The most popular are
Router information protocol (RIP) is a simple, vector-based, hop-count metric. All routers broadcast their entire RIP data base across the internet every 60 seconds, whether there are changes or not.
Open shortest path first uses a link-state algorithm that allows a router to dynamically monitor status changes of each link and broadcast those changes immediately.
Interior gateway routing protocol, developed by route vendor Cisco systems and it is an enhanced proprietary version of RIP.
Because each individual router understands the entire internet's topology, a router can automatically pick up a failed device's traffic load, there by rerouting traffic around the failed router. This network partitioning also means that the separate LAN can still function as local communication paths. A router internet is more secure than a bridged LAN because a communication device has access to the router's addressing capabilities only when needed. Router reliability is measured in mean time between failures. High end protocol routers offer redundant power supplies, hot swappable components, and fault-tolerant bus architecture.
Hybrid routers software can handle both functions. If the software cannot identify the protocol for the packet-routing request, it simply bridges the packet. Internal bridges included with such LAN operating systems as net ware and LAN manager can be used for routing functions. Each network interface card in the file server supports a different logical network.
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