Direct versus indirect routing

There are two types of routing:

direct

When a machine can send an IP packet to another machine without going through a third machine, the route the packet will travel is said to be a ``direct route'' and the selection of that route is called ``direct routing''. In ``Example internetwork'', the machine columbia can trace a direct route to any of the machines on the 10.0.118 network (that is, seine, thames, and volga). The machine columbia cannot reach london or paris directly.

Example internetwork

indirect

When a machine wishing to send an IP packet to a second machine must send that packet through a third machine, the route the packet will travel is said to be an ``indirect route'' and the selection of the intermediary machine is called ``indirect routing''. The intermediary machine, a router, has connections to more than one network and is said to provide a gateway between the networks. Therefore, a router may also be called a ``network gateway''. In ``Example internetwork'', the machine volga is a network gateway between the 10.0.118 network and the 10.0.246 network. If the machine seine needs to send an IP packet to paris, it must send the packet to volga, which forwards the packet to paris.

Sometimes the source and destination hosts are more than one network away from each other.