When you need to control how traffic leaves your data center fabric and choose the optimal exit point among multiple upstream BGP routers, use BGP Local Pref as the path attribute.
In this video, I’ll show you exactly how to set up Local preference, manipulate outbound path selection, and verify the changes inside the NX-OS BGP table.
Summary
| Feature | Description |
|---|---|
| Is it a BGP Path attribute? | Yes, it is a well-known, discretionary |
| Purpose | Identifies the best exit point from the BGP local AS to reach the external subnet (NLRI). |
| Scope | Throughout the BGP AS in which it was set, including confederation sub-ASes |
| Default value | 100 for iBGP and Null for eBGP updates |
| Changing the defaults | Not supported in Cisco devices. |
| Value range | 0 through 4,294,967,295 |
| Which is best? | Higher values are better (when comparing eBGP with iBGP routes, if the Local_Pref value is not explicitly set, BGP treats the NULL value (for the eBGP route) as the default 100 (for the iBGP route)). |
| Configuration | Using the set local-preference command in the route-map under the neighbor address-family with ‘in’ direction. |
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Additional Resources:
BGP Path Attributes: Your BGP Path Selection Master Guide
