What is a Firewall

The firewall is probably the best known security appliance. By definition firewall is a system or a group of systems which implements access policy between two or more networks.

Firewalls can be classified into four main classes:

1. Dedicated firewalls 

2. Routers integrated firewalls

3. Servers integrated firewalls 

4. Personal firewalls 


1. Dedicated firewalls are hosts that runs an operating system designed for packet filtering and addresses translation. We can exemplify PIX systems or Checkpoint. These systems are capable of sustaining a large number of connections but routing facilities are extremely limited. For a simple network , firewall can be used as a router. For more complex networks is necessary a router.

2. Firewalls integrated into routers are used to remove the previous insufficiency. This class can not sustain the same number of connections, but it does better in more complex topologies, where you need the facilities of a router. Many products provide routers integrated firewall facilities, from firewall modules for high-end routers, to extremely compact dedicated for use in SOHO networks.


Fortigate Routing

In this article i will describe some routing capabilities that Fortigate has.

Routing Protocols


Fortigate is capable of many routing Protocols:

1. Static Routes (not really a routing protocol 😉 )

2. BGP

3. RIP



The Fortigate Firewall has also a Routing table 1that displays all the learned routes and also a FIB table. You might know about FIB from the Cisco CEF.

Routing Features: 


The FIB contains all local and non-local routes that are known to the Device. It is populated by the routing table and in the High-Availability mode FIB is replicated among the clusters, but only the Master builds up the FIB, based on the routing table.

Reverse Path Forwarding (RPF)

This is used for anti-spoofing protection. You can find more about Reverse Path Forwarding here.

Bidirectional Forwarding Detection (BFD)

This is used to deal with dynamic routing protocols problems, of not having a fine granularity for detecting device failures on the network and re-routing around those failures. This works like the “hellos” of the OSPF routing protocol, but it actually connects to the router.

Default Administrative Distances for Fortigate:

1. The Fortigate Firewall assigns an AD of “20” to EBGP routes.

2. Static Routes have an AD of  “10”

3. Connected Routes have an AD of “0”

4. When you configure the BGP protocol a default route-map is created to make the AS non-tranzit (cool feature)


If you have any questions please ask.



Fortigate Conserve Mode – How to stop it and what it means

The Fortigate Firewall has more diagnostic tools, but you will mostly be faced with the following problems:

1. Conserve Mode

This problem happens when the memory shared mode goes over 80%.
To exit this conserve mode you have to wait (or kill some  of the processes) until the memory goes under 70%.

2. Antivirus FailOpen

This is a safeguard feature that determines the behavior of the Fortigate AntiVirus System, when it becomes overloaded with high traffic.

To mitigate this you have more type of options:

#set av-failopen { off | on-shot | pass | idledrop}

Below we will describe what all of them do:

a. Off – if the FG enters conserve mode, the Fortigate will stop accepting new AV sessions, but will continue to process currently active sessions


How to Pass Fortinet FCNSA

I thought it would be useful to list all my posts that are related to the Fortinet exam called FCNSA.

Here are my FCNSA Notes:

1. Fortigate Default Settings

2. Fortigate Default Protection Profiles

3. Fortigate Logging and Alerts 

4. Fortigate Antivirus and Antispam 

5. Fortigate service – Fortiguard 

6. Fortigate Authentication

7. Fortigate Antivirus

8. Fortigate Web Filtering 


Hope this helps you guys as it helped me passing my FCNSA exam.




Fortigate VDOMs

Fortigate VDOMs


What are Fortigate VDOMs(Virtual Domains)?

Well Fortigate VDOMs are like ASAs contexts, you are able to separate the firewall so it looks like you have 2, with different management and user groups. With ASA you lose some features when you enabled contexts, but in the Fortinets’ Firewall you do not lose any features.(Isn’t that just great?!)

VDOMs features:

1. Have separate routing and firewall services

2. Each physical interface belongs to only one Virtual Domains

3. By Default for the VDOMs to communicate you need an external source(Internet) to allow the communications

4. By Default 10 VDOMs are supported (in NAT or Transparent Modes)

5. The Configuration file of the Fortigate, holds all VDOM configuration. EX: AntiVirus, IPS and System Time


I. VDOM Configuration Features:


Fortigate Tutorial – Web Filtering

Fortigate Tutorial – Web Filtering


Fortigate processes Web Filtering options in the following order:

1. URL Filtering

2. Fortiguard Web Filtering

3. Content Exempt

4. Content Block

5. Script Filter

6. Antivirus


Let’s talk a little about all of them:

1. URL Filtering – you define what URLs the Fortigate can block

2. Fortiguard Web Filtering – based on the categories you choose, the Fortigate will block the pages

3. Web Content block

This option blocks specific words or patterns. You can use Perl regular expressions and the based on scores you can block those

4. Web Content Exemption – allows the administrator to override the web content block feature.

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