Tutorials & mental models.
Short, opinionated walk-throughs of the CCNA® topics that actually trip people up. New post every couple of weeks.
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- ccnacdplldplayer2
CDP vs LLDP — Cisco's Neighbor Discovery vs the Vendor-Neutral Way
The two Layer-2 discovery protocols on every Cisco lab: CDP (Cisco proprietary, on by default) and LLDP (IEEE 802.1AB, off by default). When to use which, security implications, and the show commands the CCNA tests.
Read post → - ccnafhrphsrpvrrpglbp
HSRP vs VRRP vs GLBP — Which First-Hop Redundancy for CCNA (and Real Networks)
The three FHRP options side-by-side — HSRP (Cisco, most common), VRRP (IETF, multi-vendor), GLBP (Cisco, load-balancing). Which one to configure, why, and the CCNA-blueprint corners you'll be asked about.
Read post → - ccnaaclaclsospffundamentals
Cisco Wildcard Masks: ACLs & OSPF Without Confusion
The mental model for Cisco wildcard masks. When to use them (ACLs, OSPF), how to convert from a subnet mask, and the #1 mistake that breaks half the labs.
Read post → - ccnatrunksvlansinter-vlan-routing
Cisco Trunking Best Practices (Without Causing Outages)
Learn the SOPs for configuring Cisco trunk links in enterprise networks. Avoid the common switchport trunk allowed vlan typo and master DTP and Native VLANs.
Read post → - aisecuritynetopscompliancechatgptgenai
Don't paste that config into ChatGPT — safe GenAI for netops
A senior network engineer's field guide to using LLMs for NetOps without leaking configs, keys or topology. What actually leaks in a show run, the compliance exposure, a working sanitizer script, prompt patterns that work, and enterprise + self-hosted options compared.
Read post → - ccnastpspanning-treelayer-2-securityswitchingtroubleshooting
BPDU Guard vs Root Guard vs Loop Guard — When to Use Which (CCNA)
CCNA tutorial on Cisco STP protection: BPDU Guard, Root Guard, and Loop Guard. What each blocks, where to apply them, and the real outage each one prevents.
Read post → - ccnafundamentalsnetwork-plustroubleshooting
TCP 3-Way Handshake Explained — SYN, SYN-ACK, ACK (CCNA)
The TCP 3-way handshake for CCNA: what SYN/SYN-ACK/ACK actually carry, why it's three packets not two or four, and the states Wireshark shows you.
Read post → - ccnaawscloud-networkingus-careerscertifications
CCNA vs AWS Advanced Networking — which one, when, and why
Cisco's CCNA and AWS's Advanced Networking Specialty overlap in name only. Which one fits your US networking career trajectory, whether you should do both, and the honest 2026 salary picture for cloud-focused NetEngs.
Read post → - ccnanetwork-plusus-careerscertifications
CCNA vs Network+ — which for a US networking career in 2026
Cisco's CCNA and CompTIA's Network+ overlap on paper but target different careers. Which one US employers actually want, which pays more, and which order to sit them if you're going to do both.
Read post → - ccnaospfroutingtroubleshooting
OSPF timers, DR/BDR election, and why yours is stuck in EXSTART
The three OSPF problems that trip up every CCNA candidate: timer mismatches that never form a neighbor, DR/BDR election producing an unexpected router as DR, and the classic EXSTART/EXCHANGE stall from an MTU mismatch. With show commands, real numbers, and the fixes.
Read post → - ccnaospfeigrprouting
OSPF vs EIGRP — which one for CCNA and real US networking work
A candid comparison of OSPF and EIGRP: what the CCNA 200-301 exam tests on each, where each one is actually deployed in US enterprise networks, and how to answer the interview question about picking between them.
Read post → - ccnastatic-routingrouting
Static routing — floating routes, admin distance, and defaults
Everything you need to configure static routes with confidence: next-hop vs exit-interface, admin distance, floating statics as backup, the default route ('quad zero'), and why the wrong syntax silently drops your recursive lookup.
Read post → - ccnaipv6slaacrouting
IPv6 for CCNA — SLAAC, EUI-64, and the boot sequence
The IPv6 subset the CCNA actually tests — address structure, EUI-64, SLAAC vs DHCPv6, link-local vs global, and the exact CLI commands to bring a host up on a fresh v6 network without needing a DHCP server.
Read post → - ccnaetherchannellacpswitching
EtherChannel with LACP — bundling four links into one Port-channel
How to bundle multiple switch uplinks into a single logical Port-channel so STP stops blocking your redundant cables. LACP vs PAgP vs static, mode combinations that actually form a bundle, load-balance methods, and the diagnostic commands.
Read post → - ccnaport-securitydhcp-snoopingdailayer-2-security
Layer 2 hardening — Port Security, DHCP Snooping, and DAI in one lab
The three access-layer defenses that stop 90% of L2 attacks: MAC flooding, rogue DHCP servers, and ARP spoofing. How they interact, the trust-port model, sticky-MAC pros and cons, and the diagnostic commands when something goes err-disabled.
Read post → - ccnaaclsecurity
Standard vs Extended ACL — which one to use when
A practical breakdown of Cisco IOS ACL types. When a one-line standard ACL is the right tool, when you need extended for protocol + port filtering, where to place them, and the mistakes that make ACLs silently do nothing.
Read post → - ccnahsrpfhrproutingredundancy
HSRP walkthrough — how default gateway redundancy actually works
Two routers, one virtual IP, zero downtime when the primary router dies. HSRP's active/standby election, priority, preempt, tracking, and the show commands that prove it works — plus the CCNA-favorite question about virtual MAC addresses.
Read post → - ccnaspanning-treestpswitching
Spanning Tree root bridge election — the mental model
How switches decide which one becomes the STP root bridge, what happens when priorities tie, why lowering priority is safer than lowering MAC, and how to force the root to sit where you actually want it.
Read post → - ccnaip-connectivityinter-vlan-routingsvi
Inter-VLAN Routing — SVIs vs Router-on-a-Stick (CCNA)
Free CCNA-level inter-VLAN routing tutorial for US networking learners. Why VLANs can't talk by default, router-on-a-stick with dot1Q sub-interfaces, the Layer-3 switch SVI method real networks use, and the #1 mistake that leaves SVIs up but routing dead.
Read post → - ccnaip-servicesdhcpdora
DHCP — DORA, Scopes, and the ip helper-address Relay (CCNA)
Free CCNA-level DHCP tutorial for US networking learners. The DORA exchange step by step, why every message is a broadcast, the Cisco IOS server config, ip helper-address relay across subnets, and the show commands that prove leases are landing.
Read post → - ccnaccnpsecuritydhcp-snoopingdynamic-arp-inspectionip-source-guard
Layer 2 Security — DHCP Snooping, DAI, and IP Source Guard (CCNA)
Free tutorial on Cisco access-layer security for US networking learners. How DHCP snooping, Dynamic ARP Inspection (DAI), IP Source Guard, port security and 802.1x stack together to lock down the switch port — with the config and show commands.
Read post → - ccnaip-servicesnatpat
NAT & PAT — Inside Local, Inside Global, and Overload (CCNA)
Free CCNA-level NAT and PAT tutorial for US networking learners. Static vs dynamic vs PAT/overload, the four inside/outside local/global terms decoded, the config, and the show commands that prove it works.
Read post → - ccnaexamccna-v2
CCNA v2.0 (2027) — What's Changing in the 200-301 Exam
Cisco announced the CCNA 200-301 v2.0 blueprint. Here's what changed — a new AI section, a big shift toward configuration and troubleshooting, six domains down to five — when it goes live (Feb 3, 2027), and which version you should actually study based on your exam date.
Read post → - ccnasecurityacl
Cisco ACLs — Implicit Deny, Wildcards, and the 10-Second Read
Free CCNA-level tutorial on Cisco ACLs for US networking learners. Implicit deny, wildcard masks, in vs out direction, and how to read any ACL in 10 seconds.
Read post → - ccnaswitchingvlans
VLANs Explained — Trunks, Access Ports, Native VLANs (CCNA Tutorial)
Free CCNA-level VLAN tutorial for US networking learners. Trunks, access ports, 802.1Q tagging, and native VLAN gotchas — the mental model that makes it click in 15 minutes.
Read post → - ccnaroutingospf
OSPF in 12 Minutes — The Mental Model Before the Commands (CCNA)
How OSPF actually works — the LSDB, SPF, neighbors, DR/BDR — explained as a story before you write your first router ospf 1 command.
Read post → - ccnaswitchingtroubleshootingvlanstrunks
'My Trunk Won't Pass VLAN 20' — A 6-Step Debug Workflow (CCNA)
Step-by-step troubleshooting for the classic CCNA-lab moment when you've configured the trunk but VLAN 20 traffic isn't reaching the other switch.
Read post → - ccnacareercertifications
The Free Certificates to Earn Before Your CCNA
Free Cisco and cloud certificates that thicken a junior NetEng CV before you sit the paid CCNA exam — sequenced for someone starting from help-desk or community college.
Read post → - ccnasubnettingfundamentals
Subnetting in Your Head — The Magic-Number Trick (CCNA)
The one method that turns CCNA subnetting from 'do the binary math' into 'glance at the mask, subtract, done'. Worked examples for /27, /28, /22, /21.
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