Servus Community,I run a send-only Postfix mail server on Linux Debian and run a Thor scan on it daily. ProxyShell exploitation attempt in Postfix mail server Security.You also gain additional security features by using certain public DNS resolvers (for example Google DNS, Norton DNS, or OpenDNS) to determine the best DNS forwarder you should use. someone in the middle can respond with fraudulent DNS records in place of the root hint server's response your local DNS cache can become corrupted, flush it the root hints are always under attack, your ISP, another upstream provider, or the root hint operator may automatically or manually block you from reaching it, usually temporarily as some kind of rate limiting, but sometimes permanently the root hint server list on your server is stale, and it's trying to contact ones that aren't even operating anymore Why does it suddenly stop working? there are a few reasons it can happen. The root hint servers are supposed to be used by others offering a recursive DNS service or domain hosting services, not every little company out there looking for DNS resolution.
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Root hints ARE BAD to use - they are NOT supposed to be used as your personal upstream resolver, which unfortunately is what Windows DNS service will default to. Even during this Dyn DDoS attack, I was heavily effected even using google dns. I just don't like seeing blanket "always" statements like "Root hints are garbage.
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Personally I go with forwarders as it means we can benefit from someone elses caching, plus it helps keep my config slightly simpler, if you do use forwarders though be sure to have ones from different providers (we use both google and opendns), so you can tolerate one provider having issues.Yeah I'm not at all against using public dns forwarders like google and opendns. Personally I go with forwarders as it means we can benefit from someone elses caching, plus it helps keep my config slightly simpler, if you do use forwarders though be sure to have ones from different providers (we use both google and opendns), so you can tolerate one provider having issues. Having said all this, using Root Hints isn't "bad" per-se, there isn't anything fundamentally wrong here and your servers will work either way, both options good and bad things going for them. There is also a security consideration too, with the use of forwarders you can setup strict firewall rules to only allow DNS traffic to your specified forwarders - with root hints you cannot do this as your DNS server may have to query any other DNS server to get a response. Since you are letting an upstream server handle caching it's also easier to survive events like the giant DDoS attack on Dyn last week that took out loads of major companies - since we have our forwarders pointing to opendns who were caching responses we barely noticed anything, if we had been running with root hints we would have been massively affected. On the flipside to this I've seen plenty of recommendations to use forwarders over root hints as you are only making one lookup to your forwarder vs having to query different root servers. If it has internet access, root hints are preferred. You could forward all of your dns queries to google's dns caching servers, but I've never seen or have come across a reason to have to use forwarders on a dns server that has internet access. The link I provided above is an up to date list of forwarders. It doesn't seem the forwarders are the problem. It seems like forwarders are much faster now. I remember back in the day it seemed like forwarders were slow (this could have been because of the timeout). Always use forwarders whenever possible. Hah, I would have to agree with you on this.
Root hints are garbage and depending on the OS, some of the default ones no longer work.
*** DNS-SERVER01 can't find : Server failed Questions = 1, answers = 0, authority records = 0, additional = 0ī, type = A, class = INī, type = AAAA, class = IN Header flags: response, want recursion, recursion avail. Responsible mail addr = admin.DOMAIN-NAMEī-NAME, type = AAAA, class = IN Questions = 1, answers = 0, authority records = 1, additional = 0ī-NAME, type = A, class = IN
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