Every so often I get a question from new students (and sometimes experienced ones) about the MTU in EIGRP metric calculation formula and MTU Role and whether it’s used at all or not.
Short Answer : Yes
Long Answer :
The MTU metric is only used as a tie-breaker. The formula doesn't calculate MTU value. The MTU is used if the router has to choose between multiple (equal) routes
In another words : if router would have to ignore some equal-cost paths to the same destination (the number of equal-cost paths exceeds the value of the maximum-paths router configuration parameter), it ignores those with the lowest MTU metric.