Common Routing Scenarios

Applies To: Windows 7, Windows Server 2008 R2

You can use RRAS software 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 an RRAS server that connects two local area network (LAN) segments (Networks A and B). In this configuration, a routing protocol is not required because the router is connected to all of the networks to which it needs to route packets. Routers automatically configure routes to the networks to which they are directly connected.

Multiple-router scenario

The following illustration shows a more complex router configuration. 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 communicated through the use of a routing protocol, such as the Routing Information Protocol (RIP) used for Internet Protocol version 4 (IPv4).

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 routing protocols, a network administrator must enter static routes into the routing tables of Router 1 and Router 2. Static routes 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. Networks A and B are geographically separated and, for the amount of traffic 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 connection with Router 2. The connection is maintained only as long as there are packets going back and forth. When the connection is idle, Router 1 disconnects to reduce connection costs.

Additional references

• Overview of RRAS