Network Address Translation: NAT is a methodology of mapping Private ip address to another Public ip address. Actually, private ip address can’t pass through internet without NAT. NAT provides of mapping between private ip address to route able public ip address. There are many kind of NAT and to implement depends on what our goals are for NAT and our public ip address management.
· Static NAT (One to One mapping):One to one mapping is also called static NAT it’s put a permanent ip mapping between an private ip address and a public ip address.
· NAT Overloading: It’s called Port Address Translation or PAT.In this case multiple private ip address space are able to share a common public ip address. Port address translation is reducing number of public ip address for network address translation.
· Dynamic NAT: Another NAT method are Dynamic NAT. Dynamic map puts a dynamic mapping between an internal private ip address pool and a public ip address pool.It’s also create one to one relation on a FIFO algorithm basis .This method mikrotik router called netmap.
NETMAP Configuration Example:
/ip firewall nat add chain=dstnat action=netmap to-addresses=172.16.0.0/16
dst-address=188.8.131.52/25 log=no log-prefix=""
/ip firewall nat add chain=srcnat action=netmap to-addresses=184.108.40.206/25
src-address=172.16.0.0/16 log=no log-prefix="
This configuration tell us a pool of ip address that are 172.16.0.0/16 mapped between a pool of an public ip address that are 220.127.116.11/25 is dynamically.