DNS Best Practice
You might have seen the model we use as I've described it in many places here:
We used to do it the other way, but comments by BarryG, BruceKConvergent and others convinced me to change our approach.Cheers - Bob* Caution: unchecking 'Use forwarders assigned by ISP' and failing to populate 'DNS Forwarders' will result in degraded performance as the ASG/UTM will fall back to the Root Name Servers.Change Log: 2020-02-14 Based on a post by wolfman1, I added a warning in 2. about using Google if spamhaus.org is one of the RBLs used in the SMTP Proxy; 2017-11-13 Added 2.a and 2.b based on further info in Alex Busch's thread; 2017-11-12 Added the caveat to #2 about the SMTP Proxy because of Alex Busch's comments about Content Delivery Networks (CDNs); 2017-08-02 added #8 based on a comment by Sophos' Michael Dunn; 2017-06-09 added "VPN Pool" to #1; 2017-04-08 made #3 clearer based on a question by jlbrown also added "or Google" to #5 & #6; 2017-02-12 added 188.8.131.52 comment to #2 based on a comment here by rfcat_vk; 2017-01-14 added "in the 'Domain' field" in #3; 2015-09-25 In #7 corrected #5 to #6; 2015-09-24 changed Astaro to UTM and added #7 based on comments by vilic in DNS issue?; 2015-06-22 based on a thread by TCF, I improved the wording in #1, #2 & #4; 2015-06-20 changed from .local to .loc as reminded by bimmerdriver; 2015-03-20 Added title; 2014-10-04 DHCP and internal FQDNs; 2013-10-09 Added Availability Group idea from adrienjb in #2; 2013-02-04 reordered; 2012-08-20 Added "* Caution" note for #2 based on a suggestion by BarryG
I wrote about this about5 -10 years back.
Geolocation has changed a bit since then.
Request routes, DNS Hosts and DNS Groups can help.
Don't forget Availability Groups are your friends here.
You can also make two separate AV Groups one for IPv4 and one for IPv6.
by me as a basic breakdown (insert terms as required)
Depending on size of network (How many DNS Servers you have and where you locate them (out of scope of doc)).
Primary DNS Server enabled as caching. Forwards all requests to Sophos DNS Proxy. (No DNS root lookups).
All clients point first to Primary DNS Server, (Second to Secondary Internal DNS Server if fitted), Second to Sophos Proxy if you want clients to access Internet when Primary DNS Down. (There are reasons both for and against).
Sophos DNS Proxy
I do a DNS resolve time test to the supplied ISP assigned DNS Servers to see how they perform.
Ticking 'Use forwarders assigned by ISP.
I add a Availability Group DNS IPv4 with opensource DNS Servers, using around 4-6 DNS Servers.
I add a Availability Group DNS IPv6 with opensource DNS Servers, using around 4-6 DNS Servers.
Hope this helps
Testing since 2003
SG 310 home use
Retired with Cancer
Can be contacted for those bits too hard for anybody else.
Plan to travel remote Australia to raise awareness of prostate cancer.
Have you had your PSA level checked lately.
Enjoy live you never know what is around the corner.
“Ticking 'Use forwarders assigned by ISP”
maybe my English is too bad, but if you tick / mark that checkbox the UTM will use the ISP DNS.All your other choices (availability groups and so on) won’t be considered for the DNS lookup. Just for clarification.
Have a nice day