First check what are all the interface currently in active, by using below command.
---> # ifconfig -a
Enable\Disable Network interface pcn1. you can change the interface name according to your machine.
--> # ifconfig pcn1 plumb
--> # ifconfig pcn1 plumb
--> # ifconfig pcn1 unplumb
Now we can add IP to interface pcn1
--> # fconfig pcn1 192.168.2.20 netmask 255.255.255.0 broadcast 192.168.2.255
Then bring up the interface
--> # ifconfig pcn1 up
Now additional interface is ready. but make this interface persistence on next reboot, so we need to configure some more files.
Create a new file in /etc with this format hostname.interface. add the interface IP and subnet
--> # vi /etc/hostname.pcn1
--> 192.168.2.20 netmask 255.255.255.0
And also edit and add these files /etc/inet/hosts and /etc/inet/ipnodes
--> # vi /etc/inet/hosts
--> 192.168.2.20 naachi
--> # vi /etc/inet/ipnodes
--> 192.168.2.20 naachi
note: naachi is hostname for 192.168.2.20
