5.2 NAT – Network Address Translation

IP address depletion is a main problem that facing in the public network. NAT (network address translation) is a solution that allows the IP network of an organization to appear from the outside to use different IP address then it own IP address.

Because the IP address is depletion therefore not all your hosts have global unique IP addresses. NAT technology is translates the private IP address into public IP address before sending packets to the outside network. There are two different methods, which is static and dynamic NAT.

ip nat inside source static local-ip golobal-ip – configure static NAT

ip nat [inside outside] – Enable NAT on at least one and one outside interface by interface command

ip nat pool pool name srat-ip end-ip netmask [prefix-length type rotary] - Define a pool of global addresses to be allocated as needed.

Ip nat inside source list access-list no pool pool name [overload]- Establish dynamic source translation, specifying the access list defined in the prior step. [option] overload, add the overload key word to the command

Access-listaccess-list number permit source address [source wildcard bits]

Ip nat inside destination list access-list number pool pool name – Establish dynamic inside destination translation,

Ip nat outside source list access-list no pool pool name - Establish dynamic outside source translation, specifying the access list defined in the prior step

Show ip nat translation – display the active translations

Show ip nat statistics – display

Debug ip nat [detailed] – display a line of output for each packet that gets translated.

Clear ip nat translation * - to clear all translated entries.

Clear ip nat translation inside gip lip [outside <gip> <lip>] – clear both of inside or outside translation

Clear ip nat translation outside lip gip – clear outside translation

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