I have a Cloud Provider involving me lately, as they kept getting the error below every time they tried to create an External Network in vCloud Director 9.5.

“Gateway cannot be equal to the network definition”

It was an interesting error message especially in my customer case, where they were confident of providing the right information.  It was a very small mistake that can be easily missed by others. When the above error happened, they were not using the correct Network CIDR. My customer was using 192.168.1.0/24 where he should have been using 192.168.1.1/24. Changing the CIDR to the correct one as below fixed the issue! As it was one of those simple things that others can miss, I thought I will share!