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CCNA · 200-301Beginner

IPv6 SLAAC: Prefix Not Advertised for Autoconfiguration

Hosts see the router and install a default route, but never build a global IPv6 address. Diagnose the advertised prefix and fix it yourself, live, right below.

Interactive simIPv6SLAACRouter Advertisements

Symptom

Hosts generate link-local addresses but never receive global IPv6 connectivity. Find the missing RA configuration and validate SLAAC end to end.

Your mission

Prove the cause, then fix it

Format

Guided CLI investigation

Start interactive labSee the investigation plan ↓Need a hint? Reveal the root cause ↓
IPv6 SLAAC: Missing RA Prefix Flag

Investigate before you configure.

Use the CLI evidence to isolate the fault, make the smallest safe correction, then verify the network state changed.

Observe the symptom and link state.

Diagnose by comparing the protocol evidence.

Verify the expected device state and confirm the original symptom is resolved.

Console access: R1

This workspace stacks for portrait phones. Rotate to landscape for the full split-screen console.

Need a hint?

Reveal the root cause when you're ready.

Try the investigation first, then use this as your escape hatch, not a dead end.

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Lab debrief

Turn the session into a repeatable troubleshooting pattern.

Use this reference after your attempt: first explain the symptom, then verify the evidence, then confirm the repair.

The problem

Clients receive router advertisements and install an IPv6 default route, so the router is clearly alive on the link, yet no client ever builds a global unicast address. The prefix is being advertised, but not with the flag that tells hosts to autoconfigure from it.

What you'll practice

  • Read IPv6 interface addressing
  • Recognize the role of router advertisements in SLAAC
  • Distinguish link-local from global unicast addressing
  • Verify an IPv6 default route on a client
  • Test IPv6 connectivity

The topology

One IPv6-capable router serves a single switched user LAN. The simple topology makes the RA and SLAAC exchange visible without an unrelated routing protocol.

Commands to run yourself

The real diagnostic commands for this lab, copy-paste ready. Run these in the same order to reproduce the investigation on your own session.

Inspect router IPv6 interface state
show ipv6 interface Ethernet1/0
Inspect client IPv6 configuration
ipconfig
Check IPv6 route table
show ipv6 route

Topology diagram

Frequently asked

Can a host communicate using only a link-local address?

Yes, but only on the local link. A global unicast address and default route are needed to reach other IPv6 networks.

Ready to run this lab yourself?

No setup, no image sourcing. Book a session or ask for a live demo.

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