Networking & DNS
IP addresses, reverse DNS, ports and traffic.
72 guides · page 2 of 4
DNS CNAME record explained: aliases, rules and common mistakes
What a CNAME record is, how alias resolution works, why the root domain can't be a CNAME, CNAME vs A vs ALIAS, using CNAMEs for CDNs and SaaS, and common errors.
DNS failover between servers or clouds explained
How DNS failover works with health checks and low TTLs, how it compares with floating IPs and load balancers, setting it up across two servers or providers, and its limits.
DNS over HTTPS and DNS over TLS explained
How DoH and DoT encrypt DNS lookups, how they differ from DNSSEC, browser and OS support, using them on a Linux server with systemd-resolved or Unbound, and the trade-offs.
DNS server software: BIND vs PowerDNS explained
Authoritative vs recursive DNS servers, how BIND and PowerDNS differ in storage, performance and features, what cPanel uses, and how to test a DNS server with dig.
DNS SOA and NS records explained: serial, refresh and delegation
What SOA and NS records do, every SOA field (primary NS, admin email, serial, refresh, retry, expire, negative TTL), delegation and glue, and how to check them with dig.
DNS SRV records explained: format, examples and setup
What SRV records do, the service, protocol, priority, weight, port and target fields, real examples for Microsoft 365, SIP, XMPP and Minecraft, and how to add and test them.
DNS TTL strategy for server migrations and zero-downtime changes
Choose sensible TTLs for each record type and use a lower-switch-raise plan to move a website or email to a new server with minimal downtime and no lost mail.
DNS TXT records explained: SPF, DKIM, DMARC and verification
What DNS TXT records are, how SPF, DKIM, DMARC and domain verification use them, length limits and splitting, multiple TXT records on one name, and how to check them.
DNS zone file format explained: read and write BIND zone files
Understand the structure of a DNS zone file: $ORIGIN and $TTL, the @ symbol, relative vs absolute names, record syntax, comments, and how to validate, export and import zones.
DNSSEC explained: how signed DNS works and how to enable it
How DNSSEC protects DNS answers with signatures, the chain of trust from the root, DNSKEY, RRSIG and DS records, enabling it safely, validating it and avoiding outages.
Enable HTTP/3 and QUIC in Nginx (with HTTP/2 fallback)
Turn on HTTP/3 in Nginx 1.25+: check your build, add QUIC listeners on UDP 443, advertise with Alt-Svc, open the firewall and confirm browsers really switch to h3.
Flush DNS cache on Windows, macOS, Linux and browsers
Clear cached DNS answers after changing records or moving hosts: commands for Windows, macOS, Linux (systemd-resolved, nscd, dnsmasq), Chrome and Firefox, and when flushing won't help.
Forward proxy vs reverse proxy vs load balancer
The difference between a forward proxy, a reverse proxy and a load balancer, what each is used for, real examples like Squid, Nginx, HAProxy and Cloudflare, and how they combine.
How to fix DNS SERVFAIL errors
A SERVFAIL DNS response means the resolver failed to get an answer for your domain. Learn the causes, from broken DNSSEC and dead nameservers to lame delegation, and fix it.
How to fix DNS_PROBE_FINISHED_NXDOMAIN
DNS_PROBE_FINISHED_NXDOMAIN means the domain name could not be found in DNS. Learn how to check if the domain is registered, expired or misconfigured, and fix it.
How to fix ERR_NAME_NOT_RESOLVED
ERR_NAME_NOT_RESOLVED means your browser could not turn the domain into an IP address. Learn how to fix it on your device and check the domain's DNS and registration.
How to run and read an MTR report (packet loss and latency)
Run MTR or WinMTR, then read loss, latency and jitter per hop correctly so you can tell real network problems from harmless router behaviour.
HTTP/2 and HTTP/3 (QUIC) explained: what they change and how to check them
What HTTP/2 and HTTP/3 improve over HTTP/1.1, why HTTP/3 runs on UDP, and how to check which version your site really serves with a browser or curl.
HTTPS and SVCB DNS records explained
What the new HTTPS and SVCB DNS record types do: advertise HTTP/3, alternative endpoints and ECH keys, enable alias behaviour at the zone apex, and how browsers use them.
Install a PowerDNS authoritative server with a MariaDB backend
Install the PowerDNS Authoritative Server on Linux with a MariaDB/MySQL backend, enable its HTTP API, create a zone with pdnsutil and secure the server against open recursion.
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