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Why can't we use Route Distinguisher(RD) as a tag to import and export the prefixes/routes. It is also a unique value per customer, why use the second parameter?

Not-a-Coder
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Route distinguishers are not unique to customers. It only has to be unique on the router.

Route distinguishers and route targets serve different purposes.

Route distinguishers make prefixes unique. Route targets define which prefixes get exported from or imported to VRFs.

Ron Trunk
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  • Thank you for answering my question. I understand that RD and RT serve different purposes and anyhow an engineer will configure each PE router with a unique RT value, but instead if an engineer configures a unique RD value per customer throughout the network, We can simply import and export the prefixes through the value and no need of another unique parameter RT. NOTE: I understand this is how MPLS is designed, but Wouldn't it better use a unique RD value per customer through the network to import/export prefixes to get rid of RT? – Not-a-Coder Jun 29 '20 at 11:54
  • You are assuming that RD can be used to "define" a customer, but that would be true in only the most trivial examples. A customer's routes can be in multiple VRFs with multiple RDs. Also, RD and RT values are carried in MP-BGP differently, which makes RT easier for the protocol to process. – Ron Trunk Jun 29 '20 at 11:59