Summary of "BGP - The BGP Weight Attribute"

BGP - The BGP Weight Attribute

The video titled “BGP - The BGP Weight Attribute” by Lazarus at telecomTech provides a clear and practical explanation of the BGP weight attribute, focusing on its role in BGP path selection and configuration on Cisco routers.

Key Technological Concepts and Features

BGP Overview Border Gateway Protocol (BGP) is a path vector routing protocol used on the Internet and large enterprise networks. It selects the best path among multiple routes by evaluating a sequence of attributes in a predefined order.
Weight Attribute
- A Cisco proprietary attribute, not part of the official BGP standard but widely adopted.
- It is local to the router where it is configured and not advertised to BGP peers.
- Represented as a 32-bit value, with a default of 0 for routes learned from peers and 32768 for locally originated routes.
- BGP prefers paths with higher weight values during best path selection.
Best Path Selection Process Weight is the first attribute checked. If weights are equal, BGP examines other attributes like AS_Path, etc.
Practical Example The video demonstrates a topology with two paths to the same destination (30.30.30.0/24) learned via two neighbors (R1 and R2). By default, BGP prefers the path with the shorter AS_Path (via R1). Using the weight attribute, the router is configured to assign a weight of 500 to all routes learned from R2, influencing BGP to prefer the R2 path despite the longer AS_Path. Commands shown include setting the weight on a neighbor and clearing BGP sessions (clear ip bgp *).
Granular Weight Assignment Instead of applying weight to all routes from a neighbor, a route-map can be used to assign weight to specific routes only. This allows fine-tuned control over path selection.
Use Cases and Benefits Weight is commonly used to influence outbound routing decisions on a local router. Because it is local and not propagated, it is a safe and easy method to control routing without impacting other routers.

Tutorials and Guides Provided

Explanation of the BGP weight attribute concept.
Step-by-step example of configuring weight on Cisco routers.
Demonstration of how weight affects BGP best path selection.
Mention of route-maps for more granular weight application (though detailed configuration is not shown).

Main Speaker

Lazarus from telecomTech

This summary captures the educational content focused on the BGP weight attribute, its configuration, and impact on routing decisions within Cisco-based BGP environments.