Configuring BGP Route Attributes

Configuring route attributes can change route selection results.

BGP has many route attributes. You can change route selection results by configuring attributes for routes.

BGP priority

Setting the BGP priority can control route selection between BGP routes and routes of other routing protocols.
Preferred values

After preferred values are set for BGP routes, the route with the greatest value is preferred when multiple routes to the same destination exist in the BGP routing table.
Local_Pref

The Local_Pref attribute has the same function as the preferred value of a route. If both of them are configured for a BGP route, the preferred value takes precedence over the Local_Pref attribute.
MED

The MED attribute is used to determine the optimal route for traffic that enters an AS. The route with the smallest MED value is selected as the optimal route if the other attributes of the routes are the same.
Next_Hop

BGP route selection can be controlled by changing Next_Hop attributes for routes.
AS_Path

The AS_Path attribute is used to prevent rooting loops and control route selection.
AIGP

BGP prefers the route with the smallest AIGP value during BGP route selection.

Before configuring BGP route attributes, configure basic BGP functions.

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

Setting a PrefVal for BGP Routes: After PrefVal values are set for routes, the route with the largest PrefVal is preferred when multiple routes to the same destination exist in the BGP routing table.

Setting the Default Local_Pref Attribute for the Local Device: The function of the Local_Pref attribute is similar to that of the preferred value. The priority of the Local_Pref attribute, however, is lower than that of the preferred value.

Configuring MED Attributes for BGP Routes: The MED attribute equals the metric used by an IGP. After the MED attributes of routes are set, an EBGP peer selects the route with the smallest MED value for the traffic that enters an AS if the other attributes of the routes are the same.

Configuring the Next_Hop Attribute: Configuring the Next_Hop attribute allows for flexible control of BGP route selection.

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.

Configuring Attr_Set Attribute Encapsulation or Parsing: Configuring Attr_Set attribute encapsulation or parsing ensures that the attributes of the routes sent by CEs are transparently transmitted over the backbone network.

Verifying the BGP Route Attribute Configuration: After configuring BGP route selection, verify information about route attributes.