Running your own BIND server gives you full control. Managed DNS gives you anycast, DDoS protection, and an API. Here is how to choose and how to switch.

Running your own authoritative DNS server gives you full control. Here is how to set up BIND9 for rootlog.in, create zone files, and test the setup.

Almost every 'DNS propagation delay' is actually a TTL issue. Here is how caching really works, plus /etc/hosts tricks and nsswitch.conf.

Most network problems are DNS problems. Here is a repeatable methodology for finding the root cause of any DNS issue.

A DNS zone is a database of records. Knowing how to read and query them with dig, host, and nslookup is a core sysadmin skill.

Every DNS query starts with a resolver. Understanding recursive vs iterative resolution is essential for troubleshooting and performance tuning.

DNS is the phonebook of the internet. Every lookup starts at the root servers and walks down the hierarchy — this is exactly how it works.

Preventive network health checks catch problems before they become outages. This is the daily/weekly/monthly maintenance routine every network engineer needs.

A config without a backup is a config you have already lost. The only good configuration backup is one you can restore blindfolded.

A rogue DHCP server or a spoofed ARP reply can take down an entire subnet. DHCP Snooping, DAI, and IP Source Guard are the three security layers that prevent this.

Bonding multiple physical links into a single logical channel gives you more bandwidth and redundancy. But misconfigured EtherChannel is a guaranteed loop.

A network without discovery protocols is a network you can not troubleshoot blind. CDP and LLDP give you a real-time wiring diagram from any switch.

A slow switch is often worse than a dead one. Knowing how to isolate CPU hogs, memory leaks, and error counters is what separates junior engineers from senior ones.

After a decade of fixing broken networks, certain patterns emerge. These are the most common switch misconfigurations, the outages they cause, and the commands to prevent them.

A single loop can take down an entire network in seconds. Knowing how STP works and how to troubleshoot loop-related issues is the most critical skill for any L2 engineer.

A switch fails. The replacement arrives. Every minute of downtime costs money. A documented replacement procedure ensures you can swap a switch blindfolded.

ACLs on switches filter traffic at Layer 2 and Layer 3. Port ACLs restrict host access, VLAN ACLs filter inter-VLAN traffic, and router ACLs secure Layer 3 boundaries.

The only good config backup is one you can restore blindly. Automated TFTP backups ensure you never lose a switch configuration.

Managing local passwords on every switch does not scale. AAA with TACACS+ or RADIUS centralizes authentication, authorization, and accounting for all network devices.

VLANs segment broadcast domains. Trunks carry multiple VLANs between switches. Misconfiguring either causes connectivity issues that are notoriously hard to debug.

Every switch starts as a blank slate. Setting the hostname, securing access, and enabling SSH are the first things you do before any production config.

tcpdump is the standard packet analyzer on Linux. Every senior admin uses it to capture raw network traffic and diagnose connectivity issues at the packet level.

Everything on Linux is a file. lsof lists open files and the processes that own them. ss replaces netstat with faster, more detailed socket introspection.

TCP/IP is the backbone of modern networking. Understanding how it works is essential for anyone managing servers or networks.