VLAN
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DHCP Snooping in Depth: Bindings, Option 82, and Trusted Ports
Every Layer 2 security feature worth having is built on one foundation: a table that says "this IP address,
Labs
Hands-on Cisco IOS XE lab walkthroughs. Each lab ships with a real CML topology, configs you can paste, and verified show output. Articles tagged Labs cover the full CCNA 200-301 blueprint across Network Fundamentals, Network Access, IP Connectivity, IP Services, and Security Fundamentals.
Latest
VLAN
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Storm Control: Stopping Broadcast Floods at the Port
A single misbehaving host can take down an entire VLAN. It does not take a spanning tree loop - a NIC
STP
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UDLD: Detecting Unidirectional Links Before They Loop
Spanning tree has one blind spot, and it is a dangerous one. STP decides whether to block a port based
STP
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MST and PVST+ Interoperation: The Boundary, the CIST, and the Gotchas
Two switching standards, both trying to prevent loops, neither aware the other exists. That is what an MST-to-PVST+
EIGRP
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IGP Migration: Moving from EIGRP to OSPF Without an Outage
Sooner or later somebody decides the network is moving from EIGRP to OSPF. Maybe a merger brought in a multi-
EIGRP
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Multi-Protocol Redistribution: The CCIE Scenarios That Break Networks
Redistribution between two routing protocols at a single point is easy. Redistribution between two routing protocols at two points is
EIGRP
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EIGRP over DMVPN: Multi-Hub Design and the Split-Horizon Problem
EIGRP over DMVPN works beautifully, right up until the moment you realise none of your spokes can reach any of
EIGRP
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EIGRP Offset Lists: Surgical Metric Manipulation
You have two hubs. You want every spoke to prefer HUB1 and fall back to HUB2 only when HUB1 is
EIGRP
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EIGRP Summarization with Leak Maps
Summarisation is a trade. You send one prefix instead of fifty, which shrinks the routing table and hides internal churn
EIGRP
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EIGRP Site of Origin (SoO): Loop Prevention for Dual-Homed WAN Sites
A branch office with two WAN routers is a good design. Two routers, two circuits, no single point of failure.
OSPF
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Expert OSPF Troubleshooting: Five Broken Scenarios, Ticket Style
OSPF has an unhelpful habit: when you break it, it usually says nothing. An adjacency that should form simply does
OSPF
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OSPF Path Preference: O vs O IA vs E1 vs E2 vs N1 vs N2, Proven in the Lab
Two routes to the same prefix. One has a metric of 20. The other has a metric of 31. Which