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DHCP Relay Not Working: Free ip helper-address Packet Tracer Lab
A free CCNA Packet Tracer ticket: VLAN 20 PCs get no address while VLAN 10 is fine. Work from the client to R1's ip helper-address and fix it.
CCNA
Everything mapped to the CCNA 200-301 blueprint. Articles tagged CCNA cover the exam topics in the order you actually learn them, each one backed by a lab you can build yourself.
Latest posts
TFTP vs FTP for Cisco IOS File Transfers and Config Backup
TFTP and FTP behave very differently when you copy configs and images off a router. This article backs up a real IOS XE config over both to a Linux server, with genuine transfer output and an honest speed comparison.
DHCP and DNS on Cisco Networks: Roles, Relay, and ip helper-address
DHCP discovery is broadcast and routers do not forward broadcasts, yet central DHCP servers work fine. This article builds server, relay, and client on three IOS XE routers and shows how ip helper-address makes relay work, reading state on all three.
Syslog on Cisco IOS XE: Severity Levels, Logging Host, and Real Messages
Configure Cisco IOS XE logging to a real Linux syslog server: severity levels, logging host, synced clocks, and how to read the actual messages that arrive at the collector.
SNMP Explained: v2c vs v3, OIDs, MIBs, and Real Polling
SNMP architecture explained, then put to work: polling a real Cisco IOS XE router from Linux with both SNMPv2c and SNMPv3, including what wrong credentials look like. Covers managers, agents, OIDs, and MIBs.
NTP on Cisco IOS XE: Stratum, ntp master, and Verification
Wrong device time breaks certificate validation, log correlation, and time-based auth. This article deploys NTP on real Cisco IOS XE: one router as ntp master, the others syncing to it, with genuine show output at every stage.
NAT on Cisco IOS XE: Static, Dynamic, and PAT Configuration
Static NAT, dynamic NAT, and PAT configured on a real IOS XE router in CML, with the translation table read after each one. R1 is the NAT boundary and you see exactly how each flavor rewrites addresses.
AI and Machine Learning in Network Operations
CCNA v1.1 added AI and machine learning to the blueprint. This post covers the learning types, the predictive versus generative split, real network operations use cases, and the honest limits, framed for the exam and the job.
Ansible vs Puppet vs Chef (and Terraform) for Network Automation
Ansible, Puppet, Chef, and Terraform compared on the axes that separate them, then Ansible runs for real against three live Cisco IOS XE routers, including the idempotency gotcha that bites everyone the first time.
REST APIs and JSON for Network Engineers
REST is how your scripts talk to a network controller. This guide covers HTTP verbs, status codes, authentication, and JSON structure, grounded in real requests against a live Cisco Modeling Labs controller.
Controller-Based Networking and SDN: Overlay, Underlay, and Fabric
Control plane vs data plane, northbound and southbound APIs, and the overlay, underlay, and fabric vocabulary, mapped to the Cisco products you will meet. CCNA domain 6 concepts with the routing and switching you already know kept at the center.
Password Policies and MFA for Network Devices
Harden the login prompt on Cisco IOS XE: the password-type hierarchy, minimum length enforcement, brute-force lockout, and where MFA fits, including a real brute-force attempt hitting a lab router.