Understanding RD in a VRF

Hello,

​

I am trying to understand the route distinguisher attribute and I have a question.

All the documentation I have read online state that the rd is a tag to assign to the route. For example, if VRF A has rd of 100:100, then the route of 192.168.1.0/24 will be identified as 100:100/192.168.1.0/24 in the routing process (NOT the routing table).

However, in the huge environment I am currently working with, every VRF on every router has a unique RD.

Example:

Let's say that we have this scenario : R1 --> MPLS <-- R2, and we want to configure VRF blue. The documentation states that the config should be:

vrf forwarding blue

rd 100:100

on both devices.

However, I am seeing in our production the following:

Router A:

vrf forwarding blue

rd 100:12345

and Router B:

vrf forwarding blue

rd 100:54321

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I thought that the rd was a way to identify VRFs, just like the VLAN number is for VLANs. Am I Wrong? Or is it the VRF name that is the primary key?

What is the difference/benefit of having the same rd on the same VRF on every device vs having different rd?