Attribributes combined together make up the “metric” or believability of a BGP route.
Well-Known, Mandatory
These attributes must be supported for RFC compliance.
- AS-Path
- Next-hope
- Origin
Well-Known, Discretionary
Industry standard and documented under RFC. They do not need to be included in a routing announcement but can be.
- Local Preference
- Atomic Aggregate
Optional, Transistive
Optional means that the attribute does not have to be supported in a BGP implementation – i.e. out of RFC spec. Transititive means the attibute will be passed on however.
- Aggregator
- Community
Optional, Not-Transisitive
Optional means that the attribute does not have to be supported in a BGP implementation – i.e. out of RFC spec. Non-Transititive means the attibute doesn’t need to be passed on.
- MED (Metric)
- Originator ID
- Cluster
Notes:
AS-PATH attribute can be used for loop prevention.
