In this section, we explore the world of programming, algorithms, networks, and infrastructure
This hands-on lab configures MD5 authentication on an OSPF link between two routers, verifying the neighbor relationship requires a matching key on both sides and observing the resulting failure when the keys are mismatched.
This hands-on lab configures MD5 authentication on an EIGRP-enabled interface using a key chain, verifying the neighbor relationship requires a matching key on both sides and observing the resulting failure when keys are mismatched.
This hands-on lab configures a class-map and policy-map to classify voice traffic, marks it with DSCP EF, applies a priority queue guaranteeing bandwidth for it, and verifies both the marking and queuing behavior take effect on the outbound interface.
This hands-on lab configures a complete site-to-site IPsec VPN between two routers, walking through ISAKMP Phase 1 policy, an IPsec transform set, a crypto map, and verification of both security association phases.
This hands-on lab combines a GRE tunnel with IPsec encryption, allowing a dynamic routing protocol to run across an encrypted link between two sites, something a plain IPsec VPN alone cannot support directly.
This hands-on lab configures a basic single-hub DMVPN topology using a multipoint GRE tunnel and NHRP, demonstrating how a spoke dynamically registers its physical address with the hub without requiring a separate point-to-point tunnel per spoke.
This hands-on lab configures IP SLA-based object tracking on an HSRP-enabled router, automatically lowering its priority when its WAN uplink fails, forcing failover to the standby router without requiring a full interface shutdown.
This hands-on lab presents a multi-layer connectivity failure across VLANs, trunking, routing, and NAT simultaneously, requiring systematic bottom-up troubleshooting to identify and correct three independent faults before full connectivity is restored.
This hands-on lab configures Root Guard on switch ports facing access-layer switches to prevent an unauthorized or misconfigured switch from becoming the Spanning Tree root, verifying the port enters a root-inconsistent state when a superior BPDU is received.
This hands-on lab configures BPDU Guard globally for PortFast-enabled ports and demonstrates the distinct, riskier behavior of BPDU Filter, comparing how each responds when a switch is connected to an access port that should only ever see end-user devices.
This hands-on lab configures Loop Guard on a switch's non-designated ports to prevent a unidirectional link failure from causing a Layer 2 loop, simulating a one-way BPDU loss and verifying the affected port enters a loop-inconsistent blocking state rather than incorrectly transitioning to forwarding.
This hands-on lab configures UDLD in aggressive mode on a fiber link between two switches, simulating a unidirectional fiber failure and verifying UDLD detects the mismatch and shuts down the affected port before a Layer 2 loop can form.
