NAT for IPv4

NAT for IPv4

1. NAT Characteristics

   • What is NAT?
     • Is a method of mapping an IP address space into another by modifying network address information in the IP header of packets while they are in transit across a traffic routing device
     • Address types
       • Inside address
       • Outside address
       • Local address
       • Global address

2. Types of NAT

   • Static NAT
     • constant mapping between inside local and global addresses
   • Dynamic NAT
     • dynamic network address translation allows you to automatically map inside local and global addresses
   • PAT
     • maps multiple private IPv4 addresses to a single public IPv4 address or a few addresses

3. NAT advantages and disadvantages

   • NAT conserves the legally registered addressing scheme by allowing the privatization of intranets
   • NAT provides consistency for internal network addressing schemes. NAT hides user IPv4 addresses.
   • NAT increases the flexibility of connections to the public network

4. Static NAT

   • Static NAT is a one-to-one mapping between an inside address and an outside address
   • Static NAT allows external devices to initiate connections to internal devices using the statically assigned public address
   • useful commands
     • ip nat indside source static
     • ip nat
     • show ip nat translations
     • clear ip nat statistics

5. Dynamic NAT

   • useful commands
     • ip nat pool
     • ip nat inside source list
     • show ip nat translations
   • automatically maps the inside local addresses to inside global addresses
   • uses a pool of addresses translating a single inside address to a single outside address

6. PAT

   • There are 2 ways to configura PAT
     • 1. Single ISP allocation
     • 2. Multiple public ipv4 address allocation
   • verifying PAT configurations
     • show ip nat translations
   • verify that the NAT pool has allocated a single address for multiple translations
     • show ip nat statistics

7. NAT64

   • IPv6 does provide for protocol translation between IPv4 and IPv6 known as NAT64
   • NAT for IPv6 is used in a much different context than NAT for IPv4
   • To aid in the move from IPv4 to IPv6, the IETF has developed several transition techniques to accommodate a variety of IPv4-to-IPv6 scenarios
     • dual-stack
     • tunneling
     • translation