Cisco ASA Series Cli Configuration Manual page 792

Configuring Network Object NAT
Command
Step 3
{host ip_address | subnet subnet_address
netmask | range ip_address_1 ip_address_2}
Example:
hostname(config-network-object)# subnet
10.2.1.0 255.255.255.0
Cisco ASA Series CLI Configuration Guide
1-12
Chapter 1
Purpose
If you are creating a new network object, defines the real IP
address(es) (IPv4 or IPv6) that you want to translate.
Configuring Network Object NAT