Palo Alto Interview Questions and Answers – Part II

Plao Alto Interview Questions and Answers

This post is a continuation to one of our recent post where we discussed a few questions and answers on Palo Alto firewall. Here we are adding another set of Q&A based on our readers interest. Hope this will help you in improving your knowledge of the PA firewall.

1. How to publish internal website to internet. Or how to perform destination NAT ?

To publish internal website to outside world, we would require destination NAT and policy configuration. NAT require converting internal private IP address in to external public IP address. Firewall policy need to enable access to internal server on http service from outside .We can see how to perform NAT and policy configuration with respect to following scenario Read more

Provide the access to through the public IP address from internet

Following NAT and policy rules need to be created.

NAT:-> Here we need to use pre-NAT configuration to identify zone. Both source and destination Zone should be Untrust-L3 as source and destination address part of un trust zone

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Policy-> Here we need to use Post-NAT configuration to identify zone. The source zone will be Untrust-L3 as the source address still same and the destination zone would be Trust-L3 as the translated IP address belongs to trust-l3 zone.

We have to use pre-NAT IP address for the source and destination IP address part on policy configuration. According to packet flow, actual translation is not yet happen, only egress zone and route look up happened for the packet. Actual translation will happen after policy lookup . Please click here to understand detailed packet flow in PA firewall.  Just remember the following technique so it will be easy to understand

In firewall rule,

Zone: Post NAT

IP address: Pre NAT

In NAT rule,

Zone: Pre NAT

Final Configuration looks like below:

2. What is Global Protect ?

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GlobalProtect provides a transparent agent that extends enterprise security Policy to all users regardless of their location. The agent also can act as Remote Access VPN client.  Following are the component

Gateway : This can be or more interface on Palo Alto firewall which provide access and security enforcement for traffic from Global Protect Agent

Portal: Centralized control which manages gatrway, certificate , user authentication and end host check list

Agent : software on the laptop that is configured to connect to the GlobalProtect deployment.

3. Explain about virtual system ?

A virtual system specifies a collection of physical and logical firewall interfaces and security zones.Virtual system allows to segmentation of security policy functionalities like ACL, NAT and QOS. Networking functions including static and dynamic routing are not controlled by virtual systems. If routing segmentation is desired for each virtual system, we should have an additional virtual router.

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4.Explain about various links used to establish HA or HA introduction ?

PA firewall use HA links to synchronize data and maintain state information. Some models of the firewall have dedicated HA ports—Control link (HA1) and Data link (HA2), while others require you to use the in-band ports as HA links.

Control Link :  The HA1 links used to exchange hellos, heartbeats, and HA state information, and management plane sync for routing, User-ID information and synchronize configuration . The HA1 should be layar 3 interface which require an IP address

Data Link : The HA2 link is used to synchronize sessions, forwarding tables, IPSec security associations and ARP tables between firewalls in an HA pair. The HA 2 is a layer 2 link

Backup Links: Provide redundancy for the HA1 and the HA2 links. In-band ports are used as backup links for both HA1 and HA2. The HA backup links IP address must be on different subnet from primary HA links.

Packet-Forwarding Link: In addition to the HA1 and HA2 links, an active/active deployment also requires a dedicated HA3 link. The firewalls use this link for forwarding packets to the peer during session setup and asymmetric traffic flow.

4. What protocol used to exchange heart beat between HA ?


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5. Various port numbers used in HA ?

HA1: tcp/28769,tcp/28260 for clear text communication ,tcp/28 for encrypted communication

HA2: Use protocol number 99 or UDP-29281

6. What are the scenarios for fail-over triggering ?

->if one or more monitored interfaces fail

->if one or more specified destinations cannot be pinged by the active firewall

->if the active device does not respond to heartbeat polls (Loss of three consecutive heartbeats over period of 1000 milliseconds)

7. How to troubleshoot HA using CLI ?

>show high-availability state : Show the HA state of the firewall

>show high-availability state-synchronization : to check sync status

>show high-availability path-monitoring : to show the status of path monitoring

>request high-availablity state suspend : to suspend active box and make the current passive box as active

8. which command to check the firewall policy matching for particular destination ?

>test security-policy-match from trust to untrust destination <IP>

9.Command to check the NAT rule ?

>test nat-policy-match

10. Command to check the system details ?

>show system info  // It will show management IP , System version and serial number

11. How to perform debug in PA ?

Following are the steps

Clear all packet capture settings

>debug dataplane packet-diag clear all

set traffic matching condition

> debug dataplane packet-diag set filter match source destination
> debug dataplane packet-diag set filter on

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Enable packet capture

> debug dataplane packet-diag set capture stage receive file rx.pcap
> debug dataplane packet-diag set capture stage transmit file tx.pcap
> debug dataplane packet-diag set capture stage drop file dp.pcap
> debug dataplane packet-diag set capture stage firewall file fw.pcap
> debug dataplane packet-diag set capture on

View the captured file

> view-pcap filter-pcap rx.pcap

Thanks for reading. Hope this helped in improving your Palo Alto knowledge, or clearing some of your doubts. Please let us know if you have any queries/comments.

Palo Alto Interview Questions and Answers – Part I

Plao Alto Interview Questions and Answers

Some of our readers had requested for a post with some of the common questions and answers for the Palo Alto Firewall, after reading our post on PA Firewall. Following are some of the questions normally asked for PA interview. Please use the comment section if you have any questions to add .

1. Why Palo Alto is being called as next generation firewall ?

Ans: Next-generation firewalls include enterprise firewall capabilities, an intrusion prevention system (IPS) and application control features. Palo Alto Networks delivers all the next generation firewall features using the single platformparallel processing and single management systems, unlike other vendors who use different modules or multiple management systems to offer NGFW features. Palo Alto NGFW different from other venders in terms of Platform, Process and architecture Read more

2. Difference between Palo Alto NGFW and Checkpoint UTM  ?

PA follows Single pass parallel processing while UTM follows Multi pass architecture process

3. Describe about Palo Alto architecture and advantage ?

Architecture- Single Pass Parallel Processing (SP3) architecture

Advantage: This Single Pass traffic processing enables very high throughput and low latency – with all security functions active.  It also offers single, fully integrated policy which helps simple and easier management of firewall policy

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4. Explain about Single Pass and Parallel processing architecture ?

Single Pass : The single pass software performs operations once per packet. As a packet is processed, networking functions, policy lookup, application identification and decoding, and signature matching for any and all threats and content are all performed just once.  Instead of using separate engines and signature sets (requiring multi-pass scanning) and instead of using file proxies (requiring file download prior to scanning), the single pass software in next-generation firewalls scans content once and in a stream-based fashion to avoid latency introduction.

Parallel Processing :   PA designed with separate data and control planes to support parallel processing. The second important element of the Parallel Processing hardware is the use of discrete, specialized processing groups to perform several critical functions.

  • Networking: routing, flow lookup, stats counting, NAT, and similar functions are performed on network-specific hardware
  • User-ID, App-ID, and policy all occur on a multi-core security engine with hardware acceleration for encryption, decryption, and decompression.
  • Content-ID content analysis uses dedicated, specialized content scanning engine
  • On the controlplane, a dedicated management processor (with dedicated disk and RAM) drives the configuration management, logging, and reporting without touching data processing hardware.

5. Difference between PA-200,PA-500 and higher models ?

In PA-200 and PA-500, Signature process and network processing implemented on software while higher models have dedicate hardware processer

6. What are the four deployment mode and explain ?
  1. Tap Mode : Tap mode allows you to passively monitor traffic flow across network by way of tap or switch SPAN/mirror port
  2. Virtual wire : In a virtual wire deployment, the firewall is installed transparently on a network segment by binding two interfaces together

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  1. Layer 2 mode : multiple interfaces can be configured into a “virtual-switch” or VLAN in L2 mode.
  2. Layer 3 Deployment : In a Layer 3 deployment, the firewall routes traffic between multiple interfaces. An IP address must be assigned to each interface and a virtual router must be defined to route the traffic.

7. What you mean by Zone Protection profile ?

Zone Protection Profiles offer protection against most common flood, reconnaissance, and other packet-based attacks. For each security zone, you can define a zone protection profile that specifies how the security gateway responds to attacks from that zone. The following types of protection are supported:

-Flood Protection—Protects against SYN, ICMP, UDP, and other IP-based flooding attacks.

-Reconnaissance detection—Allows you to detect and block commonly used port scans and IP address sweeps that attackers run to find potential attack targets.

-Packet-based attack protection—Protects against large ICMP packets and ICMP fragment attacks.

Configured under Network tab -> Network Profiles -> Zone protection.

8. What is u-turn NAT and how to configure ?

U-turn NAT is applicable when internal resources on trust zone need to access DMZ resources using public IP addresses of Untrust zone.

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Let’s explain based on below scenario.


In above example, the website ( statically NAT’ed with public IP address on untrusted zone. Users in the corporate office on the segment need to access the company webpage. Their DNS lookup will resolve to the public IP in the Internet zone. The basic destination NAT rules that provide internet users access to the web server will not work for internal users browsing to the public IP .

Following are the NAT rule and policy definition.

okay, not making this post too long to read. We will be adding another set of questions in our next post soon.

Thanks for reading. Hope this helped in improving your Palo Alto knowledge, or clearing some of your doubts. Please let us know if you have any queries/comments.

Click Here for Part 2 of this post, another set of questions for you.


Juniper SRX Firewall Initial Configuration

Juniper SRX is the next generation firewall designed to provides high-speed, highly effective security services—even with multiple services enabled. The firewall released with a vast range of integrated security features suitable for securing medium to large scale enterprise Data Centers. Juniper has Virtual version vSRX focusing on security of cloud infrastructure.

The following steps describe the basic configuration settings of Juniper SRX Firewall.

We will be focusing on interface configuration, zone configuration and policy configuration

Following are the topics discussing over here.

Read more

1. Initialising SRX Firewall

2. Login to the firewall using console or GUI.

3. Configuring basic settings.

4. Configure interfaces.

5. Configure Zones and zone properties.

6. Configure firewall policies.

1. Initialising SRX Firewall and Login to the firewall

  • Unpack and power on the device. 
  • Plug one end of the CAT-5e (Ethernet cable) supplied with your firewall into the RJ-45 to DB-9 serial port adapter supplied with your firewall
  • Plug the RJ-45 to DB-9 serial port adapter into the serial port on the PC
  • Connect the other end of the Ethernet cable to the console port on the services gateway.
  • Open Hyper terminal and select COM1 with following settings

Port Settings Value

Bits per second : 9600

Data bits  :       8

Parity : None

Stop bits  :       1

Flow control : None

  • Log in as the user root. No password is required at initial connection, but you must assign a root password before committing any configuration settings

2. Configuring basic settings

Start the CLI

root# cli

Enter configuration mode:

[email protected]&gt;configure


Set root password
[email protected]set system root-authentication plain-text-password

New password: password

Retype new password: password

Set admin password


[email protected]set system login user admin class super-user authentication plain-text-password

Set System host name


root# set system hostname


Set DNS Servers


root# set system name-server


root# set system name-server

Commit the configuration and login with admin user. 


3. Configure interfaces

We will use the following scenario to configure interfaces and zones.

Assign IP address for untrust interface


root#set interface ge-0/0/0 unit 0 family inet address

Assign IP address for trust interface


root#set interface ge-0/0/1 unit 0 family inet address

Configure default route


[email protected]set routing-options static route next-hop gateway

4. Configure Zones
Create untrust zone and assign interface 
root# set security zones security-zone untrust interfaces ge-0/0/0.0
Create trust zone and assign interface
root# set security zones security-zone trust interfaces ge-0/0/1.0

Enable ssh and https for firewall management on trust interface


root# set system services ssh


root# set security zones security-zone trust host-inbound-traffic system-services ssh


root# set security zones security-zone trust host-inbound-traffic system-services http


root# set system services web-management https system-generated-certificate


root# set security zones security-zone trust host-inbound-traffic system-services https


5. Configure Firewall policy

Create a firewall policy to enable all the traffic from trust zone to internet.


[email protected]set security policies from-zone trust to-zone untrust policy policy-name match source-address any 

destination-address any application any

[email protected]set security policies from-zone trust to-zone untrust policy policy-name then permit

Commit the configuration to active on the gateway.


[email protected]commit


 That’s it..! You are done with the initial configuration of a Juniper SRX firewall this system and is ready for production. Please watch this space for more posts on advanced configurations.
You may find more posts on firewall here.

Palo Alto Firewall Packet Flow

Palo Alto packet flow

The following topics describe the basic packet processing in Palo Alto firewall. Focusing beginners who are finding difficulty to understand packet flow process in Palo Alto firewall, we have tried to simplify the steps as possible.

Let’s see what happens if a new packet comes to Palo Alto firewall in the following flow-chart.

Read more

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Hope this helped you in understanding the packet flow. Please feel free to comment if you have any suggestions/questions.

You may find more posts on firewall here.


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