Controlling BGP4+ Route Selection

The policy on BGP4+ route selection can be changed by configuring BGP4+ route attributes.

Usage Scenario

BGP4+ has many route attributes. These attributes are used to define the routing policy and describe the BGP4+ route prefix. Configuring these attributes can change the policy used by BGP4+ for route selection.

Pre-configuration Tasks

Before controlling BGP4+ route selection, configure basic BGP4+ functions.

Setting the BGP4+ Priority: Setting the BGP4+ priority can control route selection between BGP routes and routes of another routing protocol.

Setting the Preferred Value for BGP4+ Routes: After the preferred value is set for BGP4+ routes, the route with the greatest value is preferred when multiple routes to the same destination exist in the BGP4+ routing table.

Setting the Default Local_Pref Attribute for the Local Device: After the Local_Pref attribute is set for BGP4+ routes, the route with the greatest attribute value is preferred when multiple routes to the same destination exist in the BGP4+ routing table. The preferred value takes precedence over the Local_Pref attribute.

Setting the MED Attribute: The MED attribute is equal to the metric used in IGP. After the MED attribute is set for routes, an EBGP peer can select a route with the smallest MED value for the traffic that enters an AS.

Setting the Next_Hop Attribute: BGP4+ route selection can be flexibly controlled by setting the Next_Hop attribute.

Setting the AS_Path Attribute: The AS_Path attribute is used to prevent routing loops and control route selection.

Configuring AIGP Attributes for Routes: The Accumulated Interior Gateway Protocol Metric (AIGP) attribute allows devices in an AIGP administrative domain to use the optimal routes to forward data.

Verifying the Configuration of BGP4+ Route Attributes: After configuring BGP4+ route attributes, verify information about the route attributes.