The default gateway IP is 10.0.2.1 (the x.x.x.1 template is used to assign the default gateway IP). For example, if you create a new virtual network for the NAT Network mode in VirtualBox and set the 192.168.22.0/24 network address, the IP address of the gateway in this network will be 192.168.22.1. You cannot change the IP address of the gateway for the network used in the NAT Network mode and change the range of IP addresses issued by the DHCP server. Similarly, the IP address of the DHCP server is 10.0.2.3 by default (the x.x.x.3 template is used).