Module 2
DNS in Operation
Why one host resolves a name and the next one does not, and what to change when a service moves.
In this module
- Trace a lookup through cache, hosts file and configured resolver
- Explain a stale answer in terms of TTL rather than luck
- Move a service without breaking the clients that reference it
Activities
Records, resolvers and the order of lookups
What answers a query, in what order, and why hosts disagree.
Lab: the service moved, the name did not
A scheduling service now lives on a different host under the same name. Make the name follow it.
Lab: a branch that cannot resolve
A branch workstation must use the central resolver across the routed WAN. Restore it.
Lab: one domain, two answers
Internal and external views of the same domain have collided. Optional, and the hardest DNS lab in the catalog.
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Curriculum topics
Each topic page lists every lesson, quiz and hands-on lab that covers it, plus how it maps onto the CCNA and Network+ blueprints.