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JNCIA-SEC and JNCIS-SEC lab 4 of 16

NAT and proxy ARP

Give Hartwell its public addressing: interface NAT, a PAT pool, a pool that keeps ports, destination NAT for the public site, static NAT for a mail relay, and proxy ARP for all of them.

Run this lab

It needs Lite: its 4 nodes are set to 5 vCPU and 7,168 MB in total. That fits the free demo too.

In your workspace: Shared, then JNCIA-SEC and JNCIS-SEC SRX security guided labs, then 04 - NAT and proxy ARP

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Level
Intermediate
Time
About 75 minutes
Nodes need
5 vCPU, 7,168 MB
Smallest plan
Lite

The scenario

Hartwell has been given a block of public addresses, 203.0.113.0/24, by its provider, and the firewall needs to use it properly. Staff should go out on a shared address, the managing director's PC on one of its own, the public site must answer on a public address, and a mail relay needs a two-way public address. Private addresses must never reach the internet: OUT has no route to them, only to its own subnet.

DeviceInterfaceAddressZone or gateway
SRXge-0/0/0203.0.113.1/24zone untrust
SRXge-0/0/110.10.10.1/24zone trust
SRXge-0/0/210.10.20.1/24zone dmz
LAN-PCeth010.10.10.10/24gateway 10.10.10.1
DMZ-WEBeth010.10.20.10/24gateway 10.10.20.1
OUTeth0203.0.113.10/24no gateway
Public addressUsed for
203.0.113.100 and .101Staff, shared with PAT (pool STAFF-POOL)
203.0.113.110Managing director's PC 10.10.10.50, ports kept (pool MD-POOL)
203.0.113.80Public web, port 80 to DMZ-WEB 10.10.20.10
203.0.113.60Mail relay 10.10.20.20, one to one

LAN-PC also holds 10.10.10.50, and DMZ-WEB also holds 10.10.20.20. The policies are in place: trust to untrust and dmz to untrust are open, so everything in this lab is about NAT. OUT's web server log shows who it thinks is calling:

tail -5 /var/log/apache2/access.log

What you’ll practise

  • State the order of NAT and policy for the first packet
  • Configure source NAT with the interface, a PAT pool and a no-translation pool
  • Configure destination and static NAT and write policies that use real addresses
  • Use proxy ARP when NAT addresses share the egress subnet
  • Prove translation from the far end and from NAT counters

The tasks

  1. Interface NAT
  2. A pool with PAT, and proxy ARP
  3. A pool without PAT
  4. Destination NAT
  5. Static NAT

The Lab Tasks pane has the scenario, these tasks, the checks to run, hints and the full solution.

Topology and devices

The network as it opens in EVE-NG, drawn from the lab’s own canvas, and the image each node runs.

Topology of NAT and proxy ARP4 nodes, 3 links. Every link is listed as text below the diagram.SRXLAN-PCDMZ-WEBOUTge-0/0/2eth0ge-0/0/1eth0ge-0/0/0eth0
4 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • SRX ge-0/0/0 to OUT eth0
  • SRX ge-0/0/1 to LAN-PC eth0
  • SRX ge-0/0/2 to DMZ-WEB eth0
Nodes in NAT and proxy ARP, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
SRXJuniper vSRX NextGen templatevsrxng-24.4R1.92 vCPU, 4,096 MB
LAN-PCEVE-NG GUI server (Docker)eve-gui-server:latest1 vCPU, 1,024 MB
DMZ-WEBEVE-NG GUI server (Docker)eve-gui-server:latest1 vCPU, 1,024 MB
OUTEVE-NG GUI server (Docker)eve-gui-server:latest1 vCPU, 1,024 MB

How to open this lab

  1. Sign in to your workspace at lab.cloudlabbox.com.

  2. In File Manager, open Shared, then the folder JNCIA-SEC and JNCIS-SEC SRX security guided labs.

  3. Open 04 - NAT and proxy ARP and start its nodes, then open Lab Tasks for the scenario and the steps.

The lab is read-only. You can start the nodes and configure the devices, but changes to the topology can’t be saved. To change it, rebuild it in your own folder.

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CloudLabBox is independent of Cisco and Juniper Networks. The lab follows exam topics and isn’t vendor training material; vendor names identify the exams and the images in the workspace.