Common Routing Scenarios

Applies To: Windows Server 2008

You can use routers in many different topologies and network configurations. This topic describes three typical routing scenarios.

Simple routing scenario

The following illustration shows a simple network configuration with a server running Routing and Remote Access that connects two local area network (LAN) segments (Networks A and B). In this configuration, routing protocols are not required because the router is connected to all of the networks to which it needs to route packets.

Simple routing scenario

Multiple-router scenario

The following illustration shows a more complex router configuration.

Multiple router scenario

In this configuration, there are three networks (Networks A, B, and C) and two routers (Routers 1 and 2). Router 1 is on Networks A and B, and Router 2 is on Networks B and C. Router 1 must notify Router 2 that Network A can be reached through Router 1, and Router 2 must notify Router 1 that Network C can be reached through Router 2. This information is automatically communicated through the use of a routing protocol, such as RIP. When a user on Network A wants to communicate with a user on Network C, the user's computer on Network A forwards the packet to Router 1. Router 1 then forwards the packet to Router 2. Router 2 then forwards the packet to the user's computer on Network C.

Without the use of routing protocols, a network administrator must enter static routes into the routing tables of Router 1 and Router 2. Although static routes work, they do not scale well to larger networks or recover from changes in the network topology.

Demand-dial routing scenario

The following illustration shows a router configuration that uses demand-dialing.

Demand-dial routing scenario

Networks A and B are geographically separated and, for the amount of traffic that is transferred between the networks, a leased wide area network (WAN) link is not economical. Router 1 and Router 2 can connect over an analog phone line by using modems (or another type of connectivity, such as ISDN) on both ends. When a computer on Network A initiates communication with a computer on Network B, Router 1 establishes a phone connection with Router 2. The modem connection is maintained as long as there are packets going back and forth. When the connection is idle, Router 1 hangs up to reduce connection costs.

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