WEIGHT Attribute
Introduction to WEIGHT Attribute
- The WEIGHT attribute is a unique attribute in BGP with distinct characteristics.
Key Characteristics
-
Not Propagated: The WEIGHT attribute is not propagated to any BGP speaker, whether eBGP or iBGP. It remains locally significant within the router where it is configured.
-
Locally Significant: The WEIGHT attribute is 100% locally significant. It influences the local router's decision-making process in selecting the best BGP route.
-
Not a BGP Path Attribute: Unlike many other BGP attributes, the WEIGHT attribute is not classified as a BGP Path Attribute. It doesn't affect BGP route advertisements or path selection across different BGP speakers.
Usage of WEIGHT
- The WEIGHT attribute is primarily used within a single router to influence the preference of BGP routes. Routers use WEIGHT to determine the best path among multiple routes to the same destination.
Additional Notes
-
Since the WEIGHT attribute is not a part of BGP's standard path attributes, it is not shared with other BGP routers. As such, it doesn't have any impact outside of the router where it is configured.
-
WEIGHT is often used in conjunction with other BGP attributes like LOCAL_PREF to fine-tune the route selection process.
Summary
- The WEIGHT attribute is a router-specific attribute used for local route preference. It has no effect on BGP route propagation between routers, making it a valuable tool for optimizing route selection within a single router.
Note
- WEIGHT is a Cisco proprietary attribute, so its usage and behavior may vary depending on the router platform.
- More information can be found here: