DNS Fortiguard in Fortigate

[unknown1020]

hi Friends, a question
Why is it not recommended to use fortiguard DNS? I have checked the FG and I have realized that it has those DNS and not from my ISP.

According to your experience, is it advisable to put the ones from google?

[srajeswaran]

Hi @unknown1020 , There are no specific disadvantages/advantages in using Fortiguard DNS servers. You can use the DNS server which has better reachability/availability.

https://www.reddit.com/r/fortinet/comments/12tf5g5/drawback_of_not_using_fortiguard_dns_besides/

[unknown1020]

but if you use the dns of fortiguard it would not be advantageous since if the fortiguard servers go down, you would have problems browsing the internet. It seems to me that two months ago there was a problem so the dns of fortiguard fell.

[srajeswaran]

It could be due to connectivity/server issues. We can use other DNS servers if there are issues with the default fortiguard DNS servers.

[Yurisk]

While it is not strictly speaking "advised against" using FortiGuard DNS servers for regular DNS queries, there are simply no benefits to using them. The common sense, on the other hand, will tell us that the disadvantages would be:

•  Unfortunately,  Fortinet's infrastructure is a bit smaller, yet, than Google (8.8.8.8) or CloudFlare (1.1.1.1), which means less DNS servers, less geographical spread of those servers, less capacity. All of this may result in high latency of the answers, and lost queries.
• Even the local ISP where the FGT is installed will be much faster to answer DNS (4-5 msec) than FTNT DNS located some 40-50 msecs away. 
• The only benefit/obligation to use FortiGuard DNS servers was for DNS Filtering to work, but it was lifted as well some 5-6 years ago, so even for that there is no benefit to using Fortiguard DNS.
• (almost forgot) Yes, you may use them if using DDNS for the FGT WAN IP resolving. 

[sw2090]

we experienced a much better performance with using local dns instead of the Fortinet ones.

We haven't yet found any problems or disadvantages with that on our FGT.