1, direct route - the configuration of the interface on the router will automatically generate a network route, the source of its own router interface. For example, the IP address of a router configuration interface 192.168.1.1/24, then the router will automatically generate routes in the 192.168.1.0/24 to this interface, as long as the interface is physically up state, the route will always exist. Letter C (Connected) identification.
2, static routing - Use command to configure the router in the routing, the source for the user to manually input. As long as the command does not disappear, the route will always exist. Letter S (Static) identification.
S * - default static route
3, dynamic routing - via dynamic routing protocols, such as the route learned RIP, EIGRP, OSPF, BGP and other sources for the router to other routers on the network neighbor each other. As long as the neighbor has always existed, the route will always exist. Letters to identify because of routing protocols.
(1) OSPF routing protocol
O E1 and O E2 is routed outside the AS
O E1 - If a distribution command used in a weight metric-type 1 E1 routing is O
O E2-- such as EIGRP redistributed into the OSPF default is O E2
difference OE1 and OE2 of:
OE1 is from an external system to the internal system METRIC It must be calculated
OE2 is calculated only within the system METRIC
O * E2-- default route outside the autonomous system
(2) RIP routing protocol
RIP routing protocol R--
R * - default routing protocols RIP