Error: "Gateway address x.x.x.x/y is not a valid IP address (Error Code: 503035)" while trying to create a new NSX segment

Products

• VMware NSX

Issue/Introduction

When attempting to create a new NSX segment and assigning a gateway IP address, the NSX Manager UI prevents the configuration from saving and displays the following error:

 

"Gateway address x.x.x.x/y is not a valid IP address (Error Code: 503035)"

 

Environment

VMware NSX

Cause

The error is caused by an invalid IP assignment attempt. In standard IPv4 networking (specifically Classless Inter-Domain Routing - CIDR), the first address of a subnet—is reserved as the Network Address which serves as a reserved identifier to represent the subnet itself and cannot be assigned to an interface (physical or virtual). NSX policy enforces standard networking RFCs to ensure routing stability; therefore, the validation logic rejects the entered address to prevent critical routing failures and conflicts within the physical and virtual network stacks.

Resolution

• Identify a Usable IP: Select an address within the subnet that is not the Network Address or the Broadcast Address.
• Modify Gateway Configuration: Change the gateway IP to a usable host address.
• Apply Changes: Save the segment configuration.