網路原理(一) RSE6 Section 3.3

classful routing
The routing table hierarchy in Cisco IOS was originally implemented with the classful routing scheme.

classless addressing
Although the routing table incorporates both classful and classless addressing, the overall structure is still built around this classful scheme.

route source (C and L)
Identifies how the route was learned. Directly connected interfaces have two route source codes. C identifies a directly connected network. Directly connected networks are automatically created whenever an interface is configured with an IP address and activated. L identifies that this is a local route. Local routes are automatically created whenever an interface is configured with an IP address and activated.

destination network
The address of the remote network and how that network is connected.

outgoing interface
Identifies the exit interface to use when forwarding packets to the destination network.

administrative distance (AD)
Identifies the trustworthiness of the route source. The AD for static routes is 1 and the AD for connected routes is 0. Dynamic routing protocols have an AD higher than 1 depending upon the protocol.

metric
dentifies the value assigned to reach the remote network. Lower values indicate preferred routes. The metric for static and connected routes is 0.

route timestamp
Identifies from when the route was last heard.

ultimate route
An ultimate route is a routing table entry that contains either a next-hop IPv4 address or an exit interface. Directly connected, dynamically learned, and local routes are ultimate routes. 

level 1 route
A level 1 route is a route with a subnet mask equal to or less than the classful mask of the network address.

level 1 parent route
A parent route is a level 1 network route that is subnetted. A parent route can never be an ultimate route. 

level 2 child route
A level 2 child route is a route that is a subnet of a classful network address.

network route
A network route that has a subnet mask equal to that of the classful mask.

supernet route
A supernet route is a network address with a mask less than the classful mask, for example, a summary address.

default route
A default route is a static route with the address 0.0.0.0/0.