Hello Samir
I understand what you’re saying here, and if you take a look at only two hosts communicating, then yes you are correct. The use of a unique ID won’t solve this problem. For this particular example, all packets that arrive at R2 will have the same source and destination IPs so any hash calculation at R2 will result in the same exit interface for all packets.
However, the use of the unique ID is not intended to solve the problem when you have only two hosts. Imagine you have 100 hosts communicating. R1 will use its hashing algorithm to load balance routing so that 50 flows go to R2 and fifty flows go to R3. Now if we use the Original or Default variation of CEF, then R2 will receive 50 flows with 50 different source IP addresses but because it uses the same algorithm as R1, it will direct them all to the same interface.
However, if we use Universal, with a unique ID, then the algorithm used by R2 will be different than the one used by R1, and will thus be able to load balance those 50 flows across multiple interfaces. I think that resolves your other questions as well, however, if not, don’t hesitate to ask follow-up or clarification questions!
I hope this has been helpful!
Laz