Chapter 9. NAT for IPV4

Chapter 9. NAT for IPV4

1. NAT Features

   • NAT is a process used by many medium and small businesses to
     • Keep IPV4 addresses
     • Provide privacy and security to end users
   • The same public IPv4 address is assigned to a host group by the shortage of addresses
   • Public and private IP addresses
   • Keep Public IPv4 addresses
   • NAT includes four types of addresses
     • Internal Local Address
       • Source address from inside the network
     • Global internal Address
       • Source address view from external network.
     • External Local Address
       • Target address view from external network
     • External Global Address
       • Target address viewed from the internal network
   • Advantages
     • Preserves the legally-registered routing scheme
     • Increases the flexibility of connections to the public network
     • Provides consistency to internal network addressing schemes
     • Provides network security
   • Disadvantages
     • Performance deteriorates
     • End-to-end functionality deteriorates
     • End-to-end IP tracking reduced
     • Tunneling becomes more complicated
     • The start of TCP connections can be interrupted

2. CARLOS MARIO HURTADO 9014114662

3. Types of NAT

   • NAT Static
     • Assigning one-to-one addresses between a local and a global address
     • Requires sufficient public addresses available
   • Dynamic NAT
     • Uses a set of public addresses and assigns them according to the order of arrival
   • PAT (Translation of the port address)
     • Assigns multiple private IPv4 addresses to a single public IPv4 address

4. Set up NAT

   • Configuring NAT Static
     • Create an assignment between the internal local address and the internal global addresses
     • Interfaces involved in translation are configured as internal or external
     • show ip nat translations
     • show ip nat statistics
   • Set up NAT dynamic
     • Enables automatic mapping of internal local addresses to internal global addresses
     • Configure internal and external interfaces involved in NAT
     • Define the set of addresses to be used for translation with the IP nat pool command
     • Set up a standard ACL to identify (allow) only those addresses to be translated
     • Connect the ACL to the set
       • ip nat inside source list access-list-number pool pool name
     • Identify which interfaces are internal to NAT
     • Identify which interfaces are external to NAT
     • show ip nat translations
     • show ip nat translations verbose
     • PAT settings
       • Address set
         • Define the global Address group
           • ip nat pool name start-ip end-ip {netmask | prefix-leght}
         • Define an ACL that allows the addresses to be translated
           • access-list number permit source [source-wildcard]
         • Specify the ACL and group that were defined to set the overload translation
           • ip nat inside source list number pool name overload
         • Identify the internal interface
           • interface tipo numero ip nat inside
         • Identify the external interface
           • interface tipo numero ip nat outside
       • Single Address
         • Define an ACL to allow traffic to be translated
         • Set up the source translation interface - overload
         • Identify internal interfaces
         • Identify the external interface
         • show ip nat translations
         • show ip nat statistics
   • Port forwarding
     • Allows an external user to reach a port in a private IPv4 address from the outside through a NAT-enabled router
     • ip-local
     • local port
     • ip-global
     • global port

5. NAT for IPV6

   • Unnecessary because there are many IPV6 addresses
   • Unique local IPV6 addresses
     • Unique local IPV6 addresses (ULA) resemble private addresses in IPV4
       • Allow sites to be merged or interconnected privately
       • They are independent of any ISP and can be used for communications within a site without having Internet connectivity
       • Cannot be routed over the Internet
       • The objective of the ULA is to provide IPV6 address space for communications within a local site

6. clear

7. debug

8. debug ip nat