Contents

NAT overview·· 1

Basic NAT concepts· 1

Basic NAT operating mechanism·· 1

Configuring outbound one-to-one static NAT· 1

Display and maintenance commands for NAT· 2

NAT configuration examples· 2

Example: Configuring outbound one-to-one static NAT· 2

NAT overview

Network Address Translation (NAT) translates an IP address in the IP packet header to another IP address. Typically, NAT is configured on gateways to enable private hosts to access external networks and external hosts to access private network resources such as a Web server.

Basic NAT concepts

The following describes basic NAT concepts:

·     NAT device—A device configured with NAT. Typically, NAT is configured on the edge device that connects the internal and external networks.

·     NAT interface—An interface configured with NAT.

·     NAT address—A public IP address used for address translation, and this address is reachable from the external network.

·     NAT entry—Stores the mapping between a private IP address and a public IP address.

Basic NAT operating mechanism

Figure 1 shows the basic NAT operating mechanism.

1.     Upon receiving a request from the host to the server, NAT translates the private source address 192.168.1.3 to the public address 20.1.1.1 and forwards the NATed packet. NAT adds a mapping for the two addresses to its NAT table.

2.     Upon receiving a response from the server, NAT translates the destination public address to the private address, and forwards the packet to the host.

The NAT operation is transparent to the terminals (the host and the server). NAT hides the private network from the external users and shows that the IP address of the internal host is 20.1.1.1.

Figure 1 Basic NAT operation

 

Configuring outbound one-to-one static NAT

About this task

Static NAT creates a fixed mapping between a private address and a public address. It supports connections initiated from internal users to the external network and from external users to the internal network. Static NAT applies to regular communications.

For address translation from a private IP address to a public IP address, configure outbound one-to-one static NAT on the interface connected to the external network.

·     When the source IP address of an outgoing packet matches the local-ip, the source IP address is translated into the global-ip.

·     When the destination IP address of an incoming packet matches the global-ip, the destination IP address is translated into the local-ip.

Procedure

1.     Enter system view.

system-view

2.     Configure a one-to-one mapping for outbound static NAT.

nat static outbound local-ip global-ip

3.     Enter interface view.

interface interface-type interface-number

4.     Enable static NAT on the interface.

nat static enable

By default, static NAT is disabled.

Display and maintenance commands for NAT

Execute display commands in any view and reset commands in user view.

 

Task	Command
Display NAT sessions.	display nat session [ { source-ip source-ip | destination-ip destination-ip } * ] [ slot slot-number ] [ verbose ]
Display static NAT mappings.	display nat static
Clear NAT sessions.	reset nat session

 

NAT configuration examples

Example: Configuring outbound one-to-one static NAT

Network configuration

Configure static NAT to allow the host at 10.110.10.8/24 to access the Internet.

Figure 2 Network diagram

 

Procedure

# Specify IP addresses for the interfaces on the device. (Details not shown.)

# Configure a one-to-one static NAT mapping between the private address 10.110.10.8 and the public address 202.38.1.100.

<Device> system-view

[Device] nat static outbound 10.110.10.8 202.38.1.100

# Enable static NAT on VLAN-interface 200.

[Device] interface vlan-interface 200

[Device-Vlan-interface200] nat static enable

[Device-Vlan-interface200] quit

Verifying the configuration

# Verify that the host at 10.110.10.8/24 can access the server on the Internet. (Details not shown.)

# Display static NAT configuration.

[Device] display nat static

Static NAT mappings:

  Totally 1 outbound static NAT mappings.

  IP-to-IP:

    Local IP     : 10.110.10.8

    Global IP    : 202.38.1.100

    Config status: Active

 

Interfaces enabled with static NAT:

  Totally 1 interfaces enabled with static NAT.

  Interface: Vlan-interface200

    Service card : ---

    Config status: Active

# Display NAT session information.

[Device] display nat session verbose

Initiator:

  Source      IP/port: 10.110.10.8/42496

  Destination IP/port: 202.38.1.111/2048

  DS-Lite tunnel peer: -

  VPN instance/VLAN ID/VLL ID: -/-/-

  Protocol: ICMP(1)

  Inbound interface: Vlan-interface100

Responder:

  Source      IP/port: 202.38.1.111/42496

  Destination IP/port: 202.38.1.100/0

  DS-Lite tunnel peer: -

  VPN instance/VLAN ID/VLL ID: -/-/-

  Protocol: ICMP(1)

  Inbound interface: Vlan-interface200

State: ICMP_REPLY

Application: INVALID

Start time: 2021-04-13 09:30:49  TTL: 27s

Initiator->Responder:            5 packets        420 bytes

Responder->Initiator:            5 packets        420 bytes

 

Total sessions found: 1