Information About Static Nat - Cisco Nexus 3548 Configuration Manual

Information About Static NAT

Information About Static NAT

Static Network Address Translation (NAT) allows the user to configure one-to-one translations of the inside
local addresses to the outside global addresses. It allows both IP addresses and port number translations from
the inside to the outside traffic and the outside to the inside traffic. The Cisco Nexus device supports Hitless
NAT, which means that you can add or remove a NAT translation in the NAT configuration without affecting
the existing NAT traffic flows.
Static NAT creates a fixed translation of private addresses to public addresses. Because static NAT assigns
addresses on a one-to-one basis, you need an equal number of public addresses as private addresses. Because
the public address is the same for each consecutive connection with static NAT, and a persistent translation
rule exists, static NAT enables hosts on the destination network to initiate traffic to a translated host if an
access list exists that allows it .
With dynamic NAT and Port Address Translation (PAT), each host uses a different address or port for each
subsequent translation. The main difference between dynamic NAT and static NAT is that static NAT allows
a remote host to initiate a connection to a translated host if an access list exists that allows it, while dynamic
NAT does not.
The figure shows a typical static NAT scenario. The translation is always active so both translated and remote
hosts can originate connections, and the mapped address is statically assigned by the static command.
Figure 5: Static NAT
These are key terms to help you understand static NAT:
• NAT inside interface—The Layer 3 interface that faces the private network.
• NAT outside interface—The Layer 3 interface that faces the public network.
• Local address—Any address that appears on the inside (private) portion of the network.
• Global address—Any address that appears on the outside (public) portion of the network.
Cisco Nexus 3548 Switch NX-OS Interfaces Configuration Guide, Release 9x
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Configuring Static and Dynamic NAT Translation