How to router learns forward a packet ….!!

Dear viewers,

Today we are discuss some important information for router platform. This concept is very important router learns how to forward a packet. I think this information is helpful our professional. So, develop our knowledge and comment………….

There are two ways a router learns how to forward a packet:

1) Static Routes;configured by the administrator manually.The administrator must also update the table manually every time a change to the network takes place.Static routes are commonly used when routing from a network to a stub (a network with a single route)network.The default route (gateway of last resort)is a special type of static route used for situations when a route is not known or is infeasible.Be creful,multiple gateways of last resorts can lead to a routing loop.To add a static route use the ROUTER command,and then the NETWORK command.

2) Dynamic Routes;routes that are automatically learned by the router after an administrator configures a router protocol.As soon as dynamic routing is enabled,the routing tables are automatically updated.dynamic routing sues broadcasts and multicasts to communicate with other routers.Each route entry includes a subnet number,the interface out to that subnet,and the IP address of the next router that should receive the packet.

Goals of routing protocols:

Dynamically learn and fill the routing table with a route to all subnets in a network.

If more than one route exists,place the best route in the routing table.

To notice when routes in the table are no longer valid,and to remove those routes  from the table.The types of router protocols that use HELLO are EIGRP,IS-IS,and OSPF.

If a route is removes from the table and another is available,to add the route to the table.

To add new routes,or replace lost routes,with the best currenetly available route as quickly as possible.

Prevent routing loops.

Routed protocols vs. routing protocols:  

Routed protocols use end nodes to encapsulate layer 3 packets along with addressing information(EX :Appletalk,IP,and IPX).

Routing protocols are used to build,share,and maintain routing tables and are used by routers (EX:OSPF and RIP).There are two basic categories of routing protocols:distance vector and link-state.