simple SNATing problems

Hallo, im from Linux world and im willing to do a SIMPLE snat on bigip ltm on linux I do that way

 

 

iptables -A POSTROUTING -s MYINTNET -j SNAT --to EXTIP

 

 

 

How can I accomplish that in big ip.

 

 

My EXTIP need to be address stated on self ips? or can I use another ip addr?

 

 

Any help?