You must specify the subnets that are used on the Grid Network.
The subnet entries include the subnets for the Grid Network for each site in your StorageGRID system, along with any subnets that need to be reachable via the Grid Network (for example, the subnets hosting your NTP servers).
If you have multiple grid subnets, the Grid Network gateway is required. All grid subnets specified must be reachable through this gateway.