Show pagesourceBack to top Share via Share via... Twitter LinkedIn Telegram Yammer RedditRecent ChangesSend via e-MailPrintPermalink × Table of Contents DNS Server implementations Fast public DNS servers Resource Records SRV Sender Policy Framework (SPF) Mail Autoconfig Test domains Dynamic DNS Free providers update DNS from DHCP Split DNS Reverse DNS lookups (rDNS) Linux Troubleshooting flush DNS cache Domain Name System (DNS) See also: Active Directory#DNS, dnsmasq DNS Server implementations CoreDNS – written in Go, Cloud Native Computing Foundation graduated project. Bind9 DNSMasq – can also do DHCP. FTL DNS ("Faster Than Light DNS") – DNSMasq fork used by Pi-hole Knot DNS – scalable DNS resolver Knot Resolver (kresd) Fast public DNS servers IP Name 9.9.9.9 Quad9 1.1.1.1 Cloudflare 8.8.4.4 Google Public DNS-2 212.82.225.12 Clara-2 DE Find out with namebench. Resource Records Format: <name> [<ttl>] [<class>] <type> <rdata> SRV https://de.wikipedia.org/wiki/SRV_Resource_Record _service._proto.name. TTL class SRV priority weight port target. Sender Policy Framework (SPF) Send mail from MX and A entries, prohibit all others: example.com 28800 TXT 10 v=spf1 mx a -all Check with spfquery. Mail Autoconfig https://tools.ietf.org/html/rfc6186 _submission._tcp SRV 0 1 587 smtp.example.com. _imap._tcp SRV 0 1 143 imap.example.com. Test domains RFC-2606 reserves 4 different TLDs for testing and documentation examples: .test .example .invalid .localhost DO NOT use .local for testing or local purposes! It's reserved for mDNS – if you hand out .local DNS entries, you'll interfere with Avahi/Zeroconf hostname resolution. Dynamic DNS Free providers no-ip.com update DNS from DHCP DNS, DDNS, and DHCP on a Linux router – Part 2 # Making the DHCP server update DNS (Mikael Hansson, oxcrag.net, 2022) Turris Omnia script DNSMasq → Kresd (for reference only, doesn't work without Turris' version of OpenWRT) Split DNS If you want to serve the same content both locally and from outside of your LAN, you can use Split DNS. A local DNS resolver responds to local clients with a LAN IP and the public DNS responds with a WAN IP. A similar thing can be done with hairpin NAT on the network layer, which routes traffic to the external IP back to the LAN. Reverse DNS lookups (rDNS) A regular lookup ("forward DNS") tells you the IP address for a given hostname. A reverse DNS lookup tells you the canonical DNS address for a given IP. This doesn't have to be populated for every IP and not all forward DNS entries also have a reverse entry. In most DNS servers this has to be set explicitly, to prevent leaking DNS names for IP addresses where this is not needed. .mail servers use this to find out if the mail hostname a system authenticates with is also the hostname which actually belongs to the system. Many mail systems discard incoming mail as spam when the reverse DNS entry doesn't point to the hostname they got mail from. rDNS entries have to be set by the provider of the IP, not the provider of the target domain. The reverse DNS database of the Internet is rooted in the .arpa top-level domain1. Linux On Linux systems, you can use dig -x $IP to look up rDNS entries. Troubleshooting flush DNS cache try one of the following: resolvectl flush-caches nmcli general reload dns-full systemd-resolve --flush-caches systemctl restart nscd systemctl restart dnsmasq systemctl restart named service networking restart [1] https://en.wikipedia.org/wiki/Reverse_DNS_lookup Last modified: 2023-08-27 00:59