When connections to multiple providers are required, BGP must select the optimum route for traffic to use. The optimum, or best, route may not be what you intended during the design, based on the design criteria, administrative policies, or corporate mandate. Fortunately, BGP provides many tools for you to influence route selection. One of these tools is the weight attribute. In this course, you will learn how to influence BGP route selection by setting the weight attribute of incoming BGP routes. Two methods that are used to set the weight attribute—default weight and route maps—are discussed in this course. You will also learn how to monitor the BGP table to verify the correct weight configuration and to properly influence path selection.

One of the attributes that BGP analyzes during the route selection process is local preference. Because of this behavior, modifying the local preference that is assigned to a route or neighbor can affect the best-path selection. Can you describe the issues that are related to maintaining consistent route selection within an AS? Can you describe how the local preference attribute can be used to affect the best-path selection process? Could you implement a local preference-based solution for neighbors in BGP? Could you implement a local preference-based solution in BGP that uses a route map to affect selected routes?

BGP provides many tools for administrators to influence route selection. You have already learned how to influence BGP route selection for outgoing traffic by setting weight or local preference. Problems can arise when administrative policies mandate a specific return path to be used for traffic that is returning to the AS. AS path prepending potentially allows the customer to influence the route selection of its service providers. In this course, you will learn about AS path prepending and the Cisco IOS commands that are required to properly configure and monitor AS path configurations. You will also learn filtering requirements for influencing route selection by using AS path prepending.

When connections to multiple providers are required, BGP must select the optimum route for traffic to use. It is equally important that the selected return path is the optimum return path into the AS. The optimum, or best, route may not be what the network designer intended based on the design criteria, administrative policies, or corporate mandate. Fortunately, BGP provides a tool, the MED attribute, that administrators can use to influence route selection. In this course, you will learn how to influence BGP route selection by setting the BGP MED attribute for outgoing BGP routes. Two methods that are used to set the MED attribute—the default MED and route maps—are discussed. In addition, you will also learn the basic MED attribute configuration, advanced commands to manipulate MED properties, as well as how to monitor and troubleshoot the BGP table to verify the correct MED configuration and to properly influence path selection.

When connections to multiple ISPs are required, BGP must select the optimum route for the traffic to use. It is equally important that the selected return path is the optimum return path into the AS. BGP provides tools for administrators to influence route selection, and the BGP community attribute is one such tool. You will learn how to influence BGP route selection by setting the BGP community attribute on outgoing BGP routes to facilitate proper return path selection. You will also learn about the configuration details of BGP communities.