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websantos
websantos
New Member
January 5, 2024
Question

Question about DNS

  • January 5, 2024
  • 1 reply
  • 984 views

Hi all,

 

I have a question about DNS...

Imagine that I have a laptop connected to the FortiGate firewall.

On the firewall, I configured two rules:

  1. The first rule allow the traffic from the laptop (192.168.1.10) to FQDN: www.fortinet.com, with the service set to 'all'.
  2. The second rule  allow traffic from the laptop (192.168.1.10) to a DNS server (10.10.10.10) with the service set to 'DNS'.

In the configuration under 'conf system DNS', I set up the DNS to be 10.10.10.10.

 

Questions:

1 . When the user opens a browser on the laptop to go to www.fortigate.com, the traffic will come to the firewall. The firewall will then send this traffic to the DNS to resolve. The DNS will resolve and tell the FortiGate the correct IP of fortigate.com. After that, because I have a rule that allows traffic to fortigate.com, will this traffic be allowed?

 

2. What other options can I use to do this?

 

 

My diagram:

diagram1.png

Thanks

 

 

1 reply

Toshi_Esumi
SuperUser
Toshi_Esumi
SuperUser
January 5, 2024

1. The browser sends a DNS query for "www.fortinet.com" to a DNS server configured/learned at the laptop first (it might not be 10.10.10.10, depending on what the laptop has) [policy #2].
2. Then the browser sends TCP SYN packets to the IP resolved by the DNS server [policy #1]. The FGT leans the IP of www.fortinet.com based on No.1.

If you run Wireshark on the laptop, you would see this flow.

Toshi

 

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