Example: Configuring Source and Destination NAT Translations

Requirements

1. Configure network interfaces on the device. See the Junos OS Interfaces Configuration Guide for Security Devices .
2. Create security zones and assign interfaces to them. See Understanding Security Zones.

Overview

This example uses the trust security zone for the private address space and the untrust security zone for the public address space. In Figure 1, the following translations are performed on the Juniper Networks security device:

• The source IP address in packets sent by the device with the private address 192.168.1.200 in the trust zone to any address in the untrust zone is translated to a public address in the range from 1.1.1.10 through 1.1.1.14.
• The destination IP address 1.1.1.100/32 in packets sent from the trust zone to the untrust zone is translated to the address 10.1.1.200/32.

Figure 1: Source and Destination NAT Translations

• Source NAT pool src-nat-pool-1 that contains the IP address range 1.1.1.10 through 1.1.1.14.
• Source NAT rule set rs1 with rule r1 to match any packets from the trust zone to the untrust zone. For matching packets, the source address is translated to an IP address in the src-nat-pool-1 pool.
• Destination NAT pool dst-nat-pool-1 that contains the IP address 10.1.1.200/32.
• Destination NAT rule set rs1 with rule r1 to match packets from the trust zone with the destination IP address 1.1.1.100. For matching packets, the destination address is translated to the IP address in the dst-nat-pool-1 pool.
• Proxy ARP for the addresses 1.1.1.10 through 1.1.1.14 and 1.1.1.100/32 on interface ge-0/0/0.0. This allows the Juniper Networks security device to respond to ARP requests received on the interface for those addresses.
• Security policy to permit traffic from the trust zone to the untrust zone.
• Security policy to permit traffic from the untrust zone to the translated destination IP addresses in the trust zone.

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

Step-by-Step Procedure

1. Create a source NAT pool.
   [edit security nat source]user@host# set pool src-nat-pool-1 address 1.1.1.10 to 1.1.1.14
2. Create a source NAT rule set.
   [edit security nat source]user@host# set rule-set rs1 from zone trustuser@host# set rule-set rs1 to zone untrust
3. Configure a rule that matches packets and translates the source address to an address in the source NAT pool.
   [edit security nat source]user@host# set rule-set rs1 rule r1 match source-address 0.0.0.0/0user@host# set rule-set rs1 rule r1 match destination-address 0.0.0.0/0user@host# set rule-set rs1 rule r1 then source-nat pool src-nat-pool-1
4. Create a destination NAT pool.
   [edit security nat destination]user@host# set pool dst-nat-pool-1 address 10.1.1.200/32
5. Create a destination NAT rule set.
   [edit security nat destination]user@host# set rule-set rs1 from zone untrust
6. Configure a rule that matches packets and translates the destination address to the address in the destination NAT pool.
   [edit security nat destination]user@host# set rule-set rs1 rule r1 match destination-address 1.1.1.100/32user@host# set rule-set rs1 rule r1 then destination-nat pool dst-nat-pool-1
7. Configure proxy ARP.
   [edit security nat]user@host# set proxy-arp interface ge-0/0/0.0 address 1.1.1.10 to 1.1.1.14user@host# set proxy-arp interface ge-0/0/0.0 address 1.1.1.100
8. Configure a security policy that allows traffic from the trust zone to the untrust zone.
   [edit security policies from-zone trust to-zone untrust]user@host# set policy internet-access match source-address any destination-address any application anyuser@host# set policy internet-access then permit
9. Configure an address in the global address book.
   [edit security address-book global]user@host# set address dst-nat-pool-1 10.1.1.200/32
10. Configure a security policy that allows traffic from the untrust zone to the trust zone.
    [edit security policies from-zone untrust to-zone trust]user@host# set policy dst-nat-pool-1-access match source-address any destination-address dst-nat-pool-1 application anyuser@host# set policy dst-nat-pool-1-access then permit

Results

From configuration mode, confirm your configuration by entering the show security nat and show security policies commands. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

If you are done configuring the device, enter commit from configuration mode.

Verification

To confirm that the configuration is working properly, perform these tasks:

• Verifying Source NAT Pool Usage
• Verifying Source NAT Rule Usage
• Verifying Destination NAT Pool Usage
• Verifying Destination NAT Rule Usage
• Verifying NAT Application to Traffic

Verifying Source NAT Pool Usage

Purpose

Verify that there is traffic using IP addresses from the source NAT pool.

Action

From operational mode, enter the show security nat source pool all command. View the Translation hits field to check for traffic using IP addresses from the pool.

Verifying Source NAT Rule Usage

Purpose

Verify that there is traffic matching the source NAT rule.

Action

From operational mode, enter the show security nat source rule all command. View the Translation hits field to check for traffic that matches the rule.

Verifying Destination NAT Pool Usage

Purpose

Verify that there is traffic using IP addresses from the destination NAT pool.

Action

From operational mode, enter the show security nat destination pool all command. View the Translation hits field to check for traffic using IP addresses from the pool.

Verifying Destination NAT Rule Usage

Purpose

Verify that there is traffic matching the destination NAT rule.

Action

From operational mode, enter the show security nat destination rule all command. View the Translation hits field to check for traffic that matches the rule.

Verifying NAT Application to Traffic

Purpose

Verify that NAT is being applied to the specified traffic.

Action

From operational mode, enter the show security flow session command.