Juniper (JUNOS) SRX – Static ‘One-to-One’ NAT

KB ID 0000995 Dtd 08/09/14

Problem

Setting up ‘Static NAT’ is the process of taking one of your ‘spare’ public IP addresses, and permanently mapping that public IP to a private IP address on your network.

Juniper SRX Static NAT

In the example above I want to give my web sever which has an internal IP address of 192.168.1.10/24, the public IP address of 1.1.1.5/24. So if someone out on the Internet wants to view my website, they can browse to http://1.1.1.5 (or a URL that I’ve pointed to 1.1.1.5 like http://www.mywebsite.com). Then that traffic will be NATTED, on the firewall for me.

Solution

1. Create a rule-set from the ‘untrust’ zone. Then add a rule to that rule-set, that has a destination of 1.1.1.5/32, and finally set it to NAT that traffic to 192.168.1.10/32.

login: root Password: *******

— JUNOS 12.1X44-D30.4 built 2014-01-11 03:56:31 UTC

root@FW-02% cli root@FW-02> configure Entering configuration mode

[edit] root@FW-02# set security nat static rule-set UNTRUST-TO-TRUST from zone untrust

[edit] root@FW-02# set security nat static rule-set UNTRUST-TO-TRUST rule NAT-RULE-1 match destination-address 1.1.1.5/32

[edit] root@FW-02# set security nat static rule-set UNTRUST-TO-TRUST rule NAT-RULE-1 then static-nat prefix 192.168.1.10/32

2. Set the firewall to proxy-arp (advertise your pubic IP address with is MAC address), then add the web server to the global address book.

Note: ge-0/0/0.0 is the physical address you are advertising the new IP address from, on firewalls in a failover cluster you would use the Reth address i.e. reth0.0

[edit] root@FW-02# set security nat proxy-arp interface ge-0/0/0.0 address 1.1.1.5/32

[edit] root@FW-02# set security address-book global address WEB-SERVER 192.168.1.10/32

3. Allow traffic OUT from the web server. Here I’m letting out all ports, if you wanted just web traffic then use the keyword junos-http (TCP Port 80 (http)).

[edit] root@FW-02# set security policies from-zone trust to-zone untrust policy WEB-SERVER-OUT match source-address WEB-SERVER

[edit] root@FW-02# set security policies from-zone trust to-zone untrust policy WEB-SERVER-OUT match destination-address any

[edit] root@FW-02# set security policies from-zone trust to-zone untrust policy WEB-SERVER-OUT match application any

[edit] root@FW-02# set security policies from-zone trust to-zone untrust policy WEB-SERVER-OUT then permit

4. Then allow traffic IN to the web server, (here I’m locking it down to just http).

[edit] root@FW-02# set security policies from-zone untrust to-zone trust policy WEB-SERVER-IN match source-address any

[edit] root@FW-02# set security policies from-zone untrust to-zone trust policy WEB-SERVER-IN match destination-address WEB-SERVER

[edit] root@FW-02# set security policies from-zone untrust to-zone trust policy WEB-SERVER-IN match application junos-http

[edit] root@FW-02# set security policies from-zone untrust to-zone trust policy WEB-SERVER-IN then permit

5. Save the changes.

[edit] root@FW-02# commit commit complete

Juniper Allowing Traffic To Custom Ports And Applications

1. Although Juniper have a lot of built in ‘applications’ you can allow, what if you want to create your own? Below I’ll create a custom application for Remote Desktop Protocol (TCP port 3389).

[edit] root@FW-A# set applications application APP-RDP protocol tcp

[edit] root@FW-A# set applications application APP-RDP destination-port 3389

2. You could now use this application in your security policies e.g.

[edit] root@FW-A#set security policies from-zone untrust to-zone trust policy TERMINAL-SERVER-IN match application APP-RDP

 

Related Articles, References, Credits, or External Links

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Author: Migrated

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