subject: Short Overview on Router [print this page] Router is network devices that link several computer networks - depending on the perspective - or disconnect. Here, the router analyses the incoming data packets by their destination address and block them or forwards them. Routed i.e., forwarded, packets arrive then either directly to the router connected to a destination network (including inter-domain) or be passed to another router in the network accessible.
Routers operate at layer 3 (network layer / network layer) of the OSI reference model. A router has multiple interfaces, the networks are reachable. These interfaces can also be virtual. On the arrival of data packets, a router must be the best way to target and thus determine the appropriate interface, via which the data is forwarded. For this he uses a locally available routing table that specifies which port on the router (or the middle) is what the net unreachable.
It is also a default route in the routing table must be available. This route on a router usually shows a higher order which is often referred to as standard and default gateway. But this is no gateway in the sense of the OSI reference model meant but just another router with any more information. Since routing tables are sorted by most systems for the precision, ie first, specific entries, and later less specific, is the default route, as a non-specific, at the end and is used for all targets that do not have more appropriate, and more specific entry in the routing table.
Some routers also command a so-called Policy Based Routing, taking the routing decision is made not only based on the destination address (Layer 3), but it will also take into account other information, such as the source address, quality requirements or parameters from higher layers like TCP (Transmission Control Protocol) or UDP (User Datagram Protocol). Thus, for example, then packages the HTTP (Web) transport, take a different path than packets with SMTP content (mail).
