Converging Remote Networks into Your Routing Table

Adam Olson

As corporate and provider networks grow their RAS (Remote Access Server) pools, a quick and reliable method of converging remote network routes needs to be implemented. Creating such a design ensures connectivity to the remote network and decreases the time before transfers can commence. This is an issue in any network where there is a possibility of a remote network connecting to more than one RAS device. You need to select the routing protocol best suited for this environment and configure all your RAS devices and routers to make sure they know who is connected to which device.

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Convergence is obtained when all the routing tables in your network are up to date and synchronized. When your systems and networks are not fully converged, traffic ends up in a black hole, arriving at a router that has no way of forwarding packets to the requested destination. This problem has obvious implications -- the remote user will not have connectivity to other networks, and the user's connection will be completely or partially unusable until full convergence has been achieved.

Convergence is not hard when the connections are from users who require only one IP address, whether dynamically or statically assigned. In this environment, static routes can be configured on the devices to point dial-in pools to the appropriate RAS device. When a static IP address is given to a user, most RAS devices will proxy ARP for the one IP address. This means that a router or host can be configured with a static route pointing out their local interface and any RAS device on that local segment will respond to ARP requests for the remote connection.<>