Routing, addressing, NAT and WAN troubleshooting

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By the end you’ll be able to

Troubleshoot IPv4 and IPv6 addressing issues, including incorrect address assignment, subnet mask or prefix length errors, duplicate addresses, invalid default gateways, APIPA addressing and misconfigured static settings.
Interpret routing tables, administrative distance, metrics and path selection behavior to identify missing routes, incorrect next hops, black holes, routing loops and asymmetric routing symptoms.

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Diagnose default gateway and inter-network reachability issues by testing local subnet communication, first-hop connectivity, end-to-end path visibility and route advertisement or static route configuration.

Troubleshoot NAT and PAT problems by validating inside and outside roles, translation rules, address pool availability, overload behavior and application symptoms caused by failed or incomplete translations.

Identify WAN troubleshooting symptoms across common link types and services, including circuit down conditions, encapsulation mismatches, clocking or carrier problems, MTU issues, provider handoff faults and loss of routing adjacency across the WAN.

Apply subnetting and addressing logic to determine whether hosts, interfaces and routed links belong to the correct network and to predict the effect of a proposed correction before implementation.

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